I made dry laundry soap last time we were home and so far so good:
10 Homemade Laundry Soap Detergent Recipes
Powdered – Recipe #9
12 cups Borax
8 cups Baking Soda
8 cups Washing Soda
8 cups Bar soap (grated)
Mix all ingredients well and store in a sealed tub.
Use 1/8 cup of powder per full load