I have a plan to have a bunch of slimes in a indoor building and kill them all after they populate so I can sell the loot but I don’t know the maximum there is.
Honestly there isn’t a practical roof I know of. I have a couple hundred or something in my basement in game and I don’t think theyve capped out or anything.
There was someone here a couple if days ago who had so many some in town that the game got too laggy to kill them. I don’t think there is a limit in game, but you might wanna check frequently that you can still move in your slime farm.