Combine shea butter and coconut oil in a heat-safe bowl. Heat a couple of inches of water over low heat in a small saucepan. Place the bowl on top to melt the oils.
Remove from heat and stir in the baking soda, corn starch/arrowroot. Add in essential oils and combine.
Pour into a small jar and let it sit until completely hardened. Replace lid and keep in a cool, dry spot.
Apply a small amount to your underarms with your fingers.