Simple starter raid farm

Small raid farm on a tower out at sea, built around one villager. You drink an ominous bottle, the raid spawns on the platform at the top, and the raiders drop down a shaft into a killing spot where you hit them through a slab gap. Because you land the killing blows you keep the hero of the village discount, which is what separates it from the fully automatic raid farms. It is ten minutes of building. The danger is real: witches heal the evokers, an evoker that survives a hit summons vexes, and several builders have lost hardcore worlds to exactly that. Java. Every raid costs one ominous bottle, so your bottle supply is the actual limit.

Do not forget the button on the block above the lava. Without it the raiders spawn on top of that block and can reach you.
Replacing the slab on the hopper with a campfire and the top slab with a full block stops vexes spawning and makes the farm run itself. You lose the emeralds, the weapons, the XP and the hero of the village buff that way.
Witches throw healing potions, so an evoker that survives one hit summons vexes. Bring a Sharpness V diamond sword to one hit them, and keep boats around to trap any vexes that do get out.
Do not bring the villager over until everything else is built. Drowned will kill him while you are up on the platform.
If the pillagers wander around on the platform instead of dropping, move the villager halfway up between where the video puts him and the top and box him in glass. Confirmed on 26.1.2.
Put a trapdoor in front of the spot you attack from, or loot comes flying out of the box past you.