This is a comprehensive explanation of how you can put together a TH9 base that will make it very difficult for all but the most elite war clans to 3 star you or whoever is using said base. This guide is not for everyone because an anti-3 star base makes the 3 star much harder than a convetional base but at a higher risk of getting 2 stared. This guide also works off of the assumption that you know the very basics of designing bases that you probably already know as a TH9 player (although it does cover a few)but if you are in a serious war clan consistently achieving 2 if not 3 star attacks on th9s meaning the enemy needs 3 star attacks to beat your clan, this is the guide for you.
~Throwing Off The Enemy~
Now due to how quickly serious war clans can find a base that gets put online, you are making it very easy for said clans to 3 star you by using a base from a youtube video or forum such as, this is due to those war clans knowing exactly where your giant bombs and teslas are located which is exactly why you want to build a base yourself. Building an anti-3 star base at th9 is no simple task but with practice and these instructions you'll be out there in war absourbing 2, 3 or more enemy war attacks with your base, or they'll just give up on attempting the 3 star.
STRATEGY NOTE: To throw off the attacker and make them think when attacking your base you need to drop the symetry as symetrical bases are much easier to attack than those that aren't.
By chaning to an anti-3 star defensive strategy as long as the enemy does not take your base for 3 stars you have succeded, this is the most effective way to ward off serious war attackers. This means that they can take the town hall, whether they do or not is irrelevant as long as they don't take everything else because they, the enemy clan, are going to have to use up 1 or multiple additional attacks to achieve 3 stars. Now the town hall can be very useful as a wall, it is the highest-HP (hit point) structure in the game so it should be used to protect high-DPS (damage per second) structures such as your archer queen, your teslas, air defense and xbows not all of them but protecting a few of the important ones will give them time to weaken the attacking troops.
~High HP Structures~
Town Hall 9 - 4600 HP
Dark elixir Storage 6 - 3200 HP (It doesn't need to be level 6 but it certainly helps)
Clan Castle 5 - 3000 HP
*It is very important to have this at level 5 as soon as posible because those extra 5 troops will make the lure and cc kill just that much harder.
*It helps if you can have it next to high damage structures but it dosent neccesarily have to be as it must be in the very center to make the lure as hard as humanly possible.
Gold & Elixir Storages 11 - 2100 HP
To have an effective setup you can not place the queen in the very middle of your base but it can be by your clan castle, it needs to be offset but at the same time you want the attacker to burn a jump spell to get to her with the killsquad. Having your queen offset will also determine where the attacker needs to send the killsquad in from to take her out because if she's in the center, the direction of the entry woulden't matter.
~Making a Difficult Lure~
Having a centuralized clan castle is one of the most important things you can do when designing your base, the more troops they have to use to lure it, the less likely they are to 3 star you, as a result, the cc (clan castle) should be the most centural building in your base.
It makes it easier to start by placing the cc on that dot in the middle then placing your less important defensive buildings such as mortars, cannons, archer towers and wizard towers in a ring such that the cc rangle only covers roughly half of each the buildings in that outer ring, this is just an example, you could use a few less buildings and have them arranged in a different manner but you want to keep hog riders and baloons from going directly into the cc raidius on the first building they hit.
(ignore the other buildings placed around that ring they're there just so I was able to save it)
~Double Giant Bombs~
To successfully defend against skilled hog-based attacks such as GoHo, Surgical Hogs, Holowiw you almost always need to have at least one set of 2 giant bombs placed side by side (see strategy note below) This will create a 2 by 4 in such a way that the attacker won't commonly trip them on an entry with a killsquad (where they go in with usually a golem, heroes and wizards to take out your cc queen and a secondary objective, either a double giant bomb set or at least one air defense). You also have to prevent the attacker from either sending a few hogs from the outside and tripping a bomb set or a group of hogs hitting a bomb set from the one of the short, 2 tile sides thereby activating 1 one the bombs and rendering that set useless.
STRATEGY NOTE: If you are a near fully maxed TH9 (maxed defenses, lv25+ heroes and near all lv10 walls you can have 4 singles but they must be placed perfectly in such a way that you can prevent an entry from taking out ANY of them and that NONE of them can be easily activated (do not put them in outside compartments but have them spread out across the base.) This will make it so that, in a hog attack, each double giant bomb will force a heal, leaving them no where else where they can heal their hogs, or use spells otherwise, this WILL NOT work consistently if you are not a very strong th9 as detailed above.
STRATEGY NOTE - 2 doubles or 2 singles and a double: Having 2 double giant bomb sets will make it so that you are twice as likely to completely vaporize a group of hogs but with 2 singles and one double each single will force a heal, so you'll have 3 spots that will force a heal over 2. It really comes down to how well each works in your base design. Personally I've seen more success in elite wars with 2 singles and 1 double but it's up to prefrence.
~Preventing losing 1 set to an entry~
To prevent losing one bomb set before the hogs even enter the playing field is by having your queen offset in a compartment with generous seperation from all of your giant bombs whether it be 2 sets, 2 singles and 1 set or 4 singles. If you have 2 doubles, put them in somewhat of a triangle with your queen, this will make it so that when the entry comes for your queen they will not take any sets or singles.
Here's an example of 2 doubles, you can see the triangle isn't ideal but it would be exeptionally difficult to kill the queen and trip a doulbe on entry with these placements (obviously this isn't finished so you would need to incorporate everything effectively for it to work effective versus a variety of attacks)
This design also shows the TH and DE storage being used as walls to protect the high DPS units such as the 2 teslas and the xbows.
For your base to work effectively in the way of having at least one set of GBs active at the same time on a group of hogs, you have to have the double/s surrounded by 2 defensive structures on the long, 4 tile sides, what you don't want is to have defensive structures by the short side because that would allow hogs for example to path to the bottom side of that middle wizard tower (see image above) causing the bottom GB to detonate at least 3 or 4 seconds before the other bomb in that set detonates allowing the hogs to stay at full health under heal, now with a proper setup such as the one above you can amost garentee that the hogs coming from the bottom archer tower or cannon will path up to either that bottom left archer tower or cannon (depending on where they're coming from) and from that cannon they'll likely split and a significant group will path into that tesla by the DE, into the middle wizard tower, then to that bottom xbow, both GBs detonate together, BAM, you've made some bacon. Same thing from the bottom left cannon, into the archer tower splitting of, significant group goes to the xbow, then the wizard tower.
~STRATEGY NOTE: Making Decoys - To have an effective war base, the attacker can't just scout your base out for 2 minutes and guess with high accuracy where your giant bombs are, this will make their attack easier and go much more smoothly making you much more likely to be 3 starred. Therefore you have to have at least 2 or 3 2x4 spaces that would likely contain a giant bomb and work well with hog pathing if they did.
Here's an example of 2 singles and 1 double:
You can see that both the singles as well as the double are at least 2 compartments in which is critical so that the attacker can't detonate one with just 4 or 5 hogs.
~Air Defense & Teslas~
In serious TH9 wars, you need to really think about where you are putting your air defense because there are quite a few strategies out there designed specifically to take advantage of bases with poor air defense placements. You can place them effectively by making it hard for the attacker to take your queen and an amount of air defense equal to the golems in their killsquad. You're going to want them at least 4 tiles from the outer wall to prevent the queen from taking any down from the outside and you should have them hard to get with your queen by protecting them with high HP buildings and teslas as you can see in the setup by that top air defense, and again be creative don't copy what you see here but make sure it they'll hold up against a killsquad so it can take down those balloons, dragons and lava hounds. In simple terms you're going to want to butt those air defense out away from the queen. They also need to cover the outside defenses as in the ones in that defensive ring around the cc from earlier in the guide so that attackers can't just send in 2 loons per defense and take out what's not in range.
To place your teslas effectively you should understand their potential, A level 7 tesla does 87 DPS, certainly a destructive force considering it only takes up a 2x2 so you can place them toger for exeptional concentrated damage. Now what you don't want to do is have a very obvious spot for a quad tesla, you'll usually find these in the cores of popular bases, you want to have several open 2x2 spots on top of the ones housing your teslas so that the attacker will be very uncertain of where your teslas acctually are. You should use them behind heavy HP buildings and/or your heroes espically your queen. Now this strategy changes if you have lower level teslas (lower than lv6), if that's the case you should use them as cc lure traps by placing them outside where attackers will likely come to lure the cc or or place them outside behind buildings to converge attacking golems.
Walls are amoung the highest HP structures at TH9, and you have 250 of them so use them to make it hard on the attacking troops by causing them to stop and have to bust one open while being bashed by your defenses as often as you can, this means you do NOT want a large ring in the middle or outside of your base or a massive compartment that the attacking troops can just run around in, this will make it so that in a ground attack even the most skilled attackers will have to wast a spell slot to jump over a junction and at least a 4 or 6 troop spaces to bust your outer wall open with wallbreakers. Also make it so that no matter where the attacker places a jump spell they will not get a lot of value out of it, you don't want the attacker opening up 3 large compartments or your queen compartment if it has an air defense or a double set (which it shoulden't but speaking theoretically because no base is perfect).
I hope this helps and if there's anything you want me to add or if you have any suggestions let me know.