Steps: Melt the cocoa butter, add colorant and fragrance, mix.
Then add powdered ingredients, stir well and pour into small molds, such as a fancy ice cube tray.
Let sit in fridge or freezer until set then pop them out of the molds onto waxed paper or parchment paper and let sit for a short while.
Store in baggies or airtight container.
Use one or two per bath, and be sure you have a non-slip mat in place, as the oils may make for a slick surface in your tub.
Note: Be sure that your"parts" are based upon weight, that the cocoa butter is melted when you weigh it, and that your"parts" are small amounts, such as a tablespoon or two.
You can also substitute the citric acid with more baking soda and/or sea salt to make non-fizzing melts, however the fizziness helps to slowly disperse your oils through your bath.