Adjustable eyelids!

I'd really love to figure out how people do them! Are there any tutorials out there? If they exist I can't find them. I know some people use magnets, but I have no idea what kind, where to get them or what to do with them. Like, do you use hot glue with them?

Any information regarding this topic would be fantastic! And like what would you make the eyelids out of? Thin foam? Thick foamy maybe?

Confused!