How can I create troll storage?

Hello there!

If you don’t know what I mean by “Troll Storage”, I’ll explain it:
For a side-project, I am working on a fangame for a game called “World of Trollge” which is basically those Jojo games but with trolls.

Anyway, you are able to store trolls and I am wondering how can I do the same thing. How can I do that?