Hypertufa molds can be almost anything, literally. I've used plastic containers from the thrift store, the recycle, or even simply a plastic bag draped over a pile of sand.
Here are some that I've saved up from various sources; I like the square with round corner types for a pot that is simple and classic. This one is an ice cream container, made of firm but flexible plastic.
The mold is lined with thin poly, molded to the corners, then the bottom is filled with hypertufa mix. The height of the sides is variable, but the higher you get, the more chance there is of it collapsing.
Dried and cured, the pot is ready to plant. There is a drain hole in the bottom, which is essential if the plants are to be healthy. Different thicknesses of poly film make different depths of creases, which gives it a great texture.
This size of pot is perfect for special succulents, geraniums or herbs.