slimes not spawning in slime farm

Solution 1:

Slimes usually take a LONG time to spawn even in swamps. Make sure your not in peacefully just in case you accidently turned it to it. Hope this helped.

Solution 2:

There are a number of issues to be aware of when building a slime farm. It is not clear from your description if you took all of them into account, so I'll list them all:

• You know slimes only spawn in certain chunks. So, no worries there, but for future readers, just making that point clear. Amidst is one excellent tool for finding spawn chunks.
• Slimes only spawn below level 40. It isn't clear if your spawning pad is below level 40 or not.
• Slimes spawn more rarely than other mobs, so you need to have a lot more slime spawnable areas than normal mob spawning areas. The typical way to accomplish this, is to light up all surrounding caves, and the entire overworld in a 128 block radius around your spawning pad.