Hello there fellow chiefs!
Let me start off by saying that this isn't an original concept thought of by myself. This idea has been around for a while, but I thought by creating a guide here (I had a quick search and couldn't find a similar guide, apologies if there is one) it would help players to understand the concept better. Guides on the "buffer" layer can be found on other websites, the supercell forums for example, but a lot of you out there may not visit it regularly, so this guide will help you.
The basic idea of a "buffer" layer is to create a space large enough between the outer defences and the central defences so that those pesky little piggies go round in a circle destroying only the outer defences, causing them to get hit by traps along the way while taking heavy fire from those central defences. Not only does this allow you more time to weaken them, but those oh so very powerful heal spells become of less use, as they will be used up on the outer defences. This works best for TH10, but can be done successfully with TH9, depending on the attackers skill. Note- This guide/plan are solely for defending against those mass hog attacks. It may leave you susceptible to other attacks. From attacks that I have received using my plan below, my base dealt well Giant/Healer combos as well as mass Giants and tier 1 troops. I have not yet received a GoWiWi or GoWiPe attack as I am farming in Gold 2/3.
Now onto the more 'technical' information.
To understand how this works, you first need to understand the game mechanics of the Hog Rider. After destroying a defence building, they move on to the closest one in terms of game tiles. Something to consider is that they are not in the centre of the defence they just destroyed, they are on the outside, so what's the shortest distance to the next defence building? When placing your outer ring of defences, make sure that the distance between two of them is shorter than the distance from one defence building in the outer ring to a defence building in the centre.
Before we go any further, my plan can be found here - plan/311429
After looking at my plan, you can see that in the central defences I have placed my two x-bows both set to ground (more on this later), along with the Clan Castle and DE storage. These for obvious reasons. I have also chosen to place my Gold Storages (Gold>Elixir for me, can be swapped if you want) along with the Wizard Towers, again for obvious reasons. Lastly I have placed an AD, to help out with those all air attacks. The reason I chose to set the x-bows to ground only is so they could reach the hogs all the way around the hog-ring or outer defence layer.
The "buffer" layer is the most important layer. Too small, and the hogs will reach the centre very quickly and make the base useless. Too big, and there may not be enough fire power to weaken them significantly before they reach the centre. It is all about trial and error, finding out what works best for you. As you can see from my plan, the buffer layer consists of the non-defence buildings that are most important to you. If your heroes are not placed in the centre layer, then placing them in the buffer layer is a must. It makes them harder to lure and takes more time, both of which can help towards deterring an attacker. I also placed the other storages, for me elixir, as well as my DE pumps and some Gold Mines.
The outer layer is just a ring made up of less important defence buildings that attracts the hogs all the way around. By placing traps in-between them, it further helps to weaken the hogs meaning the attacker has to use up his heal spells more quickly. In my plan I have chosen to place the Giant Bombs in groups of two, as by having two level 4 Giant Bombs together, it can wipe out a group of hogs with ease (and has done on many occasions for myself). The placement of the air Bombs is entirely up to yourself, after a few air attacks or Healer attacks, you will start to notice where they attack from and can place them accordingly.
The final layer is just made up of the other buildings. Barracks, Army Camps, Spell Factory etc all go here. If you are making my plan, then you can swap the plan from a farming layout to a hybrid by replacing the Laboratory with the Town Hall.
Now this base isn't entirely hog proof. Unless you are a level 10 TH with 2 level 3 Inferno Towers and max defences will you be able to stop mass hogs easily. A group of 30+ level 5 Hog Riders with 4 level 6 heal spells can easily 100% you. It all depends on different factors. Did they lure your cc? did they die by traps? Did they infiltrate the centre layer too quickly/easily? Again, a little trial and error will help here.
I have written this guide quickly so I apologise for any grammatical errors or information that I may have missed. If you require any more information or have any questions, feel free to comment below and I will reply as soon as possible.
Again to conclude, I understand this is not an original concept and many of you may have thought of this by yourself. I am merely putting it out there to the people that haven't yet came across the idea and would like a little help in defending against hog attacks.
Happy clashing :-)