Put the salt, baking soda and citric acid into a medium mixing bowl and stir until well combined. *Add any coloring to the mixing bowl until you've achieved your desired color.
Put the castile soap, sweet almond oil and essential oils into a small mixing bowl or measuring cup and whisk to combine.
Carefully, pour the soap and oil mixture into the bowl with the dry ingredients. Gently stir to combine. It will bubble up, but do your best to stir as gently as possible.
Once it's well combined, dump it out onto a parchment paper lined cookie sheet to dry. I would suggest dividing it up between two cookie sheets to speed the drying process. It took a few days for mine to dry on one cookie sheet.
As your fizzing bath salts mixture begins to dry, you can break it up into smaller and smaller pieces to help it dry faster.
Once it's completely dry, transfer it to a mixing bowl and use a meat tenderizer or potato masher to break the clumps into smaller pieces that resemble Pop Rocks candy.
As long as the mixture is completely dry, you can transfer it to mason jars for storage. This recipe makes about two pints (or four 8-ounce jarof Pop Rocks fizzing bath salts.
To use, add 1/2 to 1 cup of your Pop Rocks fizzing bath salts to your bath water.