Getting into micro nations

Hi! I don’t know if this is the right flair, but for awhile now, I been wanting to get more into micro nations, either making my own, working for one, or visiting other micro nations. I live in Canada Ontario, and I got some questions.

How do I know what one is unclaimed? And following that question, do you need to sign some sort of form to start one on certain land? And also can it be anywhere? Or does it need to be unclaimed? I’m not the best at explaining. Also sorry if this post isn’t allowed here.