This guide seeks to teach the player how to create a villager trading hall.
Purpose
Villager trading halls maximize the number of villagers that can be easily reached. They also provide a way to quickly discard unwanted villagers and replace the ones that are discarded. They can take the form of a literal "hall", with villagers lined up and waiting for the player to trade with them.
Mechanics
There are three parts to a villager trading hall: the input, storage, and output.
Input
The villagers for a trading hall generally come from a villager breeder. A source anywhere else is impractical given the amount of effort exerted to transport villagers out of a village.
The mechanism that puts the villager into the hall must be able to close off the cell once the villager enters, to prevent more villagers from entering that cell. The mechanism must then open the next cell to allow for a villager to enter.
Storage
Sometimes, the player will want to keep a villager because it has valuable or worthwhile trades. These villagers must be accessed, so they stay in separate "cells" until a better villager comes along; at which point the player may wish to discard them. They must be protected from zombies, lightning, and other things that could bring harm to them. The villagers must also have workstation blocks nearby, so that they can restock their trades.
Output
A villager may come along with undesirable trades, or no trades at all. Also, a better villager might come along that would replace one that already exists in the hall. At this point, the player may wish to discard the villager, and the trading hall must provide a way to do so.
This discarding mechanism must be able to remove the villager from the cell and then open it up to allow for more villagers to drop in.
Once a villager is discarded, it is up to the player to do what they want with them. The most common thing to do is move the discarded villagers into one area, where they are killed by whatever means suits the player. It is not recommended to kill them manually, because that will lower the player's popularity, and if the popularity gets too low, any iron golems of that village become hostile toward that player. An alternative to killing the discarded villagers is to store them for an iron golem farm, put them into a village, or put them to work in farms and breeders.
Designs
Reason: Videos
Designs come in all shapes and sizes, but they all have the same basic parts, as described above.
Note: These videos are outdated as most of design not work after the Village & Pillage Update, due to villagers needing to work with their corresponding job site block to resupply their trades and can only resupply up to twice per day. Also, villagers now need to level up to unlock new trades.
Mysticat's Design
Here is a 1.16 design that is super compact, low resource, and infinitely tileable
Tango Tek's Design
(Java Edition only; does not work on Bedrock)
sZPeddy's Design
LogicalGeekBoy's Design (after village and Pillage update)
(Java Edition only)
Useful Villagers
Butcher:
Butchers buy raw meat for emeralds. Very useful if you have animal farms. They also buy dried kelp blocks and sweet berries, easy-to-farm items. They sell cooked meat, which is useful if you don't want to use your coal, wood, or lava for cooking food.
Farmer:
Farmers buy crops for emeralds. The best to trade are carrots and potatoes, because using fortune on the crop gives more carrots and potatoes respectively. This doesn't work on wheat or beetroot, as it only drops more seeds.
Fisherman:
To a beginning player, a fisherman's trades can be expensive, such as the villager buying coal and string for emeralds. However, they can cook fish for you and sell campfires. A master level fisherman will buy a boat for an emerald, meaning that 2 logs can get you an emerald. Also, 3 emeralds can be used to buy a bucket of cod. A bucket is worth much more than 3 emeralds. They can even sell an enchanted fishing rod.
Librarian:
Until you have a very good sugarcane farm, the librarian's paper trade won't be worthwhile. However, one librarian can sell up to 3 enchanted books, which can be useful early game. You can enchant tools with an anvil, or disenchant them to get bonus experience.
Cleric:
Clerics sell exotic items, such as redstone, lapis lazuli, glowstone, and bottles of enchanting. They buy rotten flesh, which is a good way of getting rid of your accumulated rotten flesh. It is not recommended to depend on a cleric for emerald, because gold and nether wart are hard to farm, especially early game.
Stone Mason:
Stone Masons buy clay, stone, and other rocks. It is a way of getting a lot of emeralds, as you get lots of cobblestone when mining. However, don't trade too much clay and other rocks, as other rocks are hard to farm until you have a bartering farm. You need quartz to craft other rocks. Clay is not renewable in BE, and it is hard to farm.
Shepherd
Shepherds have one of the cheapest job site blocks. They sell one colored wool for 1 emerald, and you have a chance of getting brown, black, or white wool, which you need to give the villager 18 to get one emerald. The only useful trade would be buying shears, which cost 1 emerald. You can also sell dye, which is very easy to obtain if you have a large supply of bonemeal.
Leatherworker
Leatherworkers have very bad trades, they sell leather armor for an expensive price. However, they can sell a saddle at master level. If the villager doesn't sell a saddle, it is recommended to discard it, unless you have a large supply of leather you want to trade.
Cartographer
Cartographers buy paper and glass panes. Glass panes are easy to get if you have a auto smelter and a highly enchanted shovel. They also sell banner patterns, and explorer maps.
Fletcher
Fletchers are very useful villagers. They buy sticks, which can get you a large amount of emeralds. 32 sticks means 4 logs can get you one emerald. They sell enchanted bows and crossbows.
Blacksmith
The three professions below belong in this category. They buy the same things, coal, iron, diamond, and lava. They all sell bells. Don't depend on them for getting emerald, because coal and iron are hard to farm, and diamond and lava are nonrenewable.
Toolsmith
Sells stone, iron, and enchanted diamond tools. They always sell an enchanted diamond pickaxe at master level.
Weaponsmith
Sells iron and enchanted diamond swords and axes.
Armorer
Sells iron, chainmail, and diamond armor. The diamond armor is enchanted, and you will get up to two different pieces. Chainmail boots and helmets cost one emerald. When combined with the fletcher's stick trade, or the fisherman's boat trade, you can literally carve wood into iron. ( Get an emerald from a boat or 32 sticks. Buy chainmail boots/helmet and smelt it in a furnace. You get an iron nugget from 2-4 logs.
How to decorate your trading hall
Even though you can create the long hall with villagers locked up inside, you can design your trading hall to make it look nicer.
Farmers
Make a barn and build the long hall inside. Give the villagers some crops and farmland. Sort them so you know which villager sells/buys what. You can also give your farmers more freedom. Have one area with beds, and another area with farmland, crops, and composters. Make sure the villagers buy the crops you want. Break and replace the composter until you get the trade you want. If you traded with that villager, he cannot change his trades. Have private farms outside the farmers' pen, and use those to get crops and sell them for emeralds.