I use to make my own detergent. You can buy soda ash at a pool supply store if you can't find it in the grocery store. I started with the shaved laundry soap dissolved in water with borax and soda ash to the dry powder recipe. I made it because I was on a tight budget and it helped not having to pay for laundry detergent. I never liked it that much and haven't made any in years. I have a great recipe for dishwashing detergent that I still use when I run out of Cascade and don't know it.
1/4 teaspoon liquid dish detergent and 1/2 teaspoon baking
soda dissolved in 1/2 cup warm water and poured into the 2
detergent cups in the dishwasher. Works like a charm.
Use white vinegar in the rinse agent cup if you use this all the time.