Slimes spawn in random underground chunks below Y=39 at any light level, and can also spawn in Swamp Biomes at night depending on the phase of the Moon. They spawn more frequently during a full Moon, and never spawn during a new Moon.

Do slimes spawn at bedrock?

Minecraft Forums

since slimes only spawn in certain chunks, you might want to recreate your farm in different areas. Nothing can spawn on bedrock. They implemented that to prevent mobs from spawning on the roof of the Nether.

Why are no slimes spawning in my slime chunk?

Slimes don't spawn when a player is under 24 blocks. Slimes will also instantly despawn if a player is not under 128 blocks. Slimes only spawn below layer 40. Make sure you are in the right location.