Use a standard cheese grater to grate 1/3 of a bar of natural soap into a stock pot.
Pour 6 cups of water into the stock pot, and heat the pot over medium heat for five minutes, or until the soap melts into the water. Stir the mixture occasionally.
Pour in 1/2 cup of borax and 1/2 cup of washing soda. Stir the mixture for five minutes to incorporate all the ingredients.
Pour 10 cups of water into a 10-gallon bucket, then pour in the soap mixture. Pour in an additional gallon of water. Stir the mixture with a long-handled spoon for five minutes.
Add 2 tbsp. of your choice of essential oils into the mixture, then stir the mixture with the spoon for five minutes to incorporate the scented oil into the soap.
Place a lid onto the 10-gallon bucket, and allow the mixture to sit undisturbed for 24 hours. Use 1/2 cup of the scented oil laundry soap per load of laundry.