What do you use as hides for your ball pythons?

I like using clay flower pot bases/saucers. They are readily available, cheap, can be purchased glazed so they are easy to clean, and can be purchased in a wide variety of diameter and height to accommodate a wide variety of BP sizes. The only negative is they don’t come with a hole in the side and one must be made or the substrate built up to allow the snake to gain access.

I've also purchased plastic pencil cases from the dollor store for my small snake, cut them in half along the hinge, cut a hole in each, and have a hot and cold hide.