[Works on Mobile] Click the breeding structure, then click two monsters. Wait for the monster you bred. Click on it once it has bred then wait for it in the nursery. Once it's done incubating, click on it and you have a new monster! Then you can start breeding all over again until you have them all. You need 3 monsters to unlock the Toe Jammer. You need 7 monsters to unlock the Slimold. For breeding and incubating, the timer needs to count up to 100 for it to be done. All monsters take the same time. Ignore the eggs, idk how to fix them.
Credits to @superchixnugget for the asset for Slimold. Credits to @Wannacollab543 (Deleted account) for the Collabsters.