Board Thread:General Discussion/@comment-26581304-20150929051849/@comment-7326455-20150929061538

Well, a two-element monster still has an 80% chance of finding slime, and only takes two hours, but yeah, that seems to be about as fast as you can get things. I've so far never gotten two of the same thing at once. It's a little bit tedious.

If you want monsters to (maybe) stop asking for slime, just push "new order" - it's the left-hand button when you have a monster selected. It takes half an hour, but it'll generate a new set of requested items.