I’m currently planning a lesson, and for it, I’ll need an object. I have a pretty good idea what it should look like: It’s a smooth surface, about 2-4 feet across. It’s mostly flat, but it has a smooth, symmetric bulge in the middle. It should be something that masking tape will stick to, and likewise, it should not be damaged by tape being removed from it. It should be safe for children, both it from them and them from it. Ideally, it’d be thin, so it could be turned over and have a matching depression on the other side. And it should be something that I can cheaply get three or four of.
Is there any common object that matches this description? Alternately, what would be a good way to make one? I’m thinking maybe one could take a sheet of plexiglass, support it at the edges, and heat it in the center, but I’m not sure how well that would work. Would I need a form to shape it into, or would it just droop into shape on its own?