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.

Where can I find slime bedrock?

Slimes spawn in the Overworld in specific "slime chunks" below layer 40, regardless of light levels. They can also spawn in swamp biomes between layers 50 and 70 in light levels of 7 or less.

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.