For many years I used a very similar recipe in my front loading machine. BUT … I did not cook anything!
I finely grated one bar of Fels or Zote soap, added 2 cups of washing soda, 2 cups of Borax and 2 cups of baking soda. Mix well and use ⅛ to ¼ cup (or even more, if needed) to the wash. I generally use a warm wash and a cold rinse with white vinegar instead of fabric softener.
No cooking, no boiling water, no blender … just a lot of grating while I watched TV.