It's very simple:
Equal parts Washing Soda, Borax and Oxiclean
Note- The oxiclean is probably not essential. I use it because I wash our cloth diapers. Also as shown in my pictures below, you only need 3 tablespoons for your biggest loads. I'm not lying, if it can clean poopy diapers, I'm sure it can get your dirty knickers clean. You could also probably add some essential oils like lavender if you wanted scented clothes. I prefer unscented to keep my migraines at bay!
Jar I bought from Salvation Army.
It can hold 1 cup of each ingredient.
I put the top on and shake it up!
I use 3 tablespoons for large loads and 2 for medium.