Gather all your materials. You’ll need just soap bits, a plastic bottle, a grater, a cutting tool, and a pan for melting.
Cut the bottom off of the plastic bottle to create a mold for your new soap bar. If you have a lot of soap saved up, you may need several bottles to use as molds. You can also choose to use large sized ice cube molds, or other fun-shaped molds if you have them.
Next grate your bits of soap. When the pieces get very small, you can use the exacto knife, other cutting tool, to cut up the remaining bit into chunks.
As an added touch, you can choose to separate the colors of the grated soap, so that you can make colored layered in your new bar.