Grate your Fels-Naptha soap bar (I just used a cheese grater) and add to boiling water. Stir continuously over medium low heat until soap dissolves and is melted.
Fill your 5 gallon bucket half full with HOT tap water, add melted soap, washing soda, and borax and stir well until all powder is dissolved.
Fill the bucket the rest of the way to the top with hot water, stir, cover, and let sit overnight to thicken.
The next day, stir well and fill an old laundry detergent container with detergent.If desired, add your essential oils at this point! I use Doterra citrus bliss.
Video
Notes
Shake well before each use, because detergent can separate a bit.
Top load machines use ½ cup per load, front load machines use ¼ cup per load.