A Sister in the Ward posted this recipe on our facebook group. She makes it once a year or so as part of their food supply.
Homemade laundry soap recipe:
1 box Purex Softening Crystals (optional. I don't use because I make my own softener)
1 Box of Washing Soda
1 Box of Borax
3 Bars of Fels-naptha Soap
... 2 Tubs of Oxy Clean (generic is fine)
2 Cups Baking Soda
Slice bars of Fels into chunks and add (with a scoop of Oxy Clean) into a food processor or blender to grind till mostly smooth. Add all ingredients into a large tub (outside. powder can waft a bit). Mix well with large spoon. Add to gallon sized Ziplock bags or whatever storage devices you prefer. (I like large glass jars, but my mom just leaves it in a Tupperware tub all mixed.)
TADA. That's it. Easy peasy.
You can get everything on this list at Wal-Mart for around $30.