Clarice asked me about a reference I made in another post to lining molds with Coro-plast sheets (plastic sign material from Lowe’s or other big-box hardware stores). This may be old news, but it might help someone. Here’s the concept: You cut half way through the sheets using an Exact-O, then flip it over and fold the flaps up to make sides. Duck Tape closes the corners. It’s smooth, sturdy, and reusable.