Some kind of template- you can do a search on the internet for "skeleton hand templates" and find all kinds or draw one yourself.
Lightly use glue-stick to attach the template to the back of the contact paper and cut the shape out.
Gently peel the template paper off and re-glue it FRONT SIDE DOWN to the back of a second piece of contact paper (so you have opposite hands).
Peel the paper backing off the contact paper and stick it to a clean dry surface.
Of course! Use common sense- don’t stick it a priceless heirloom but the fridge, a mirror or a door all work well.