Place roughly half a cup of baking soda into a bowl. Add 2 tablespoons of liquid soap (plus 15-25 drops of rosemary fragrance oil, if using) and mix until well combined. At this point the texture will be like toothpaste. Add the remaining 1 cup of baking soda to the bowl and cut in using a fork just like you would when making a pie crust or biscuits.
Add 1/2 a cup of washing soda and and 3 tablespoons of crushed rosemary. Fluff and stir with a fork until well combined. Transfer to an air tight container.