In a large bowl, combine baking soda, epsom salt, cornstarch, and citric acid. Sprinkle in coloring pigment, if using, then mix well.

In a small bowl, combine melted coconut oil, essential oils, and water.

Add the coconut oil mix SLOWLY to the dry ingredients, then mix until combined. It should be a similar consistency to wet sand, and it should stick together.

Pack one half of your bath bomb mold and fill it half way with the bath bomb mixture. Place toy in the center. Fill the second half of the bath bomb mold with your mix. Close the bath bomb and press firmly to seal. Set aside and repeat for remaining 3 bath bombs.

Let bath bombs set for 24 hours before removing mold. Store in a glass container for up to 6 months.