Grate two 10-oz. bars of mild soap over a large plastic container. Use a soap that does not contain dyes or perfumes.
Add 1 cup washing soda and 1 cup boric acid powder, which you might find in grocery stores as 20 Team Mule Borax, to the plastic container.
Stir the ingredients together with a wooden spoon until they are incorporated well. Cover the plastic container with a matching lid or plastic cling wrap to prevent any moisture from entering.
Add the clothing to the washing machine and measure out enough powder based upon the size of the load or how soiled it is. For smaller loads, sprinkle 1 tbsp. of the mixture over the clothing. For a larger load or one that is very soiled, use 2 tbsp. of the homemade laundry soap.
Wash the clothing according to the label's directions.