I built a slime farm on my survival server with 7 layers (gnembom design) and no slkmes seem to be spawning. I havent spawn proofed the area yet, where am i supposed to afk? When i afk above it, the lowest platcorms are more than 32 blocks down but if i get closer down the top platforms wont work. Can someone help me out?
I think slimes don't stop moving if they're more than 32 blocks from the player.
(Unless that's changed.)
So most of them should hop off the platforms to their doom before they despawn.
Or you could look into the design with an iron golem luring them into a cactus, you can't have as many layers since you need room for the golem on top of the cactus but I think spawn proofing is more important than maximizing spawning space.
Though if there are other people on the server it would be hard to ensure that mobs don't spawn near them.
Removing everything in the chunk above the spawning platforms is supposed to improve spawning rates but that doesn't do much for you unless you can kill off the slimes that have already spawned fast enough.
I don't really know what your farm looks like or what your area looks like but I see a few problems. Spawn proofing is definitely a big thing, especially in caves. There is a maximum amount of mobs that can spawn in one world and the caves may be taking it all up. If your above-ground isn't fully lit that could be a problem too (under mountains and such). MOBS SPAWN IN A 128 BLOCK RADIUS, INCLUDING IN SPOTS YOU CANNOT SEE.
As for the top layer not spawning slimes, it could because mobs don't spawn in near players in a 24 block radius. The 24 block radius includes 24 blocks up and 24 blocks down. You might be too close to the farm.
A simple way to fix the mob cap thing is to have the afk spot be 128 blocks away from the very bottom of the farm. This will exclude a lot of the caves from the spawn radius. Since a slime farm is typically a chunk wide and thick let's say 110 blocks away. This won't exclude all of the cave interrupting your farm but it will get a lot of it. However, I think your best bet is lightning up all the dark spots under you for if you want to make future projects with mobs.