Fels-Naptha Soap. Very inexpensive and located in the laundry soap aisle.
Instructions
Step 1. You will need a large container to mix everything in. I like to use a 5-gallon bucket. Grate the soap and add to the bucket along with the other ingredients.
Step 2. Stir the mixture together. If the container has a lid, you can shake it to combine. Finally, store in a container in the laundry room.