If you're using essential oils, add 30-60 drops to 1 tablespoon Natrasorb powder and stir to combine. Set aside.
Add a small amount of oatmeal (2-3 tablespoons) to a clean coffee grinder and grind into a fine powder. Transfer the ground oatmeal to a small bowl and complete the process until all the oatmeal is in powder form.
In a medium bowl, add the coconut milk powder, baking soda, ground oatmeal and flower petals if you're using them.
Add the Natrasorb powder (if using) to the bowl with the rest of the ingredients.
Stir everything together until well-combined, then spoon the homemade milk bath mixture into your containers.
Decorate with gift label, bakers twine, etc. if desired.
Fill the tub with warm water. If you're adding essential oils that have been mixed with castile soap, do that while the water is running.
Next, add the homemade coconut milk bath. How much you use is really up to you - I typically use between 1/2 cup and a cup.
Use your hands to mix the milk bath into the water, then soak for 15-30 minutes.
Shelf Life: If you use essential oils the shelf life will be shorter (about six months). If you don't include essential oils the shelf life is pretty stable (at least a year).