Lava drop raid farm

A raid farm built on a platform over open ocean. Raiders spawn in a small cage at the top, fall down a shaft into lava at the bottom, and you finish them off from the killing spot for the drops. A villager, two beds and a bell make the village that lets a raid start, and you trigger every raid yourself by drinking an ominous bottle. Output is totems of undying, emeralds, raider gear and XP. It is not an AFK farm, you drink a bottle and swing a sword for each raid. Slab placement at the top decides whether it works at all, and the design gets mixed reports: plenty of builders have it running, plenty of others get raids that cancel or spawns that land on the wrong block.

The single slab at the top of the spawn cage has to be a bottom slab, not a top slab, or raids cancel. Keep the villager on the right side.
If the raid bar fills and then vanishes, drink the bottle and climb the ladder, wait high up until the bar fills, then go back down. Do it again at the start of every wave.
Ravagers often survive because their hitbox misses the lava, so you have to go up and kill them. Putting lava on all four sides helps.
Raiders that hit the lava on the way down burn to death instead of dying to you, and mobs killed that way drop nothing, which is why the loot is inconsistent.
The on-screen list is wrong on lava. You need 2 lava buckets, not 1, and the creator confirmed it in a reply.
Totems only drop on hard difficulty. On easy you get emeralds and gear and no totems at all.