To make a mold for an object of your choosing, you will need a container, or a box. We often use pre-made containers such as the base of a milk carton, a Tupperware or a yogurt cup, but you can also make your own at home. We usually make our own boxes so they are more of an exact fit to our object, and we use cardboard, foam core, plexiglass or wood. You can make your box any way you want and with any material that will not stick to the silicone mold, and as long as it is waterproof. For example, cardboard sticks to Mold Making Material, so we cover our cardboard boxes in packing tape before placing the object and pouring the silicone. This allows the mold to easily pull away from the box when the silicone cures. A milk carton on the other hand, already has a shiny interior and is waterproof, so no packing tape or sealing is necessary.