1 Fels Naptha soap bar, grated
1 cup washing soda
½ cup borax

Grate soap bar into small saucepan. Cover with hot water. Cook over medium-low heat, stirring continually, until soap completely dissolves.
Put washing soap and borax in a 5-gallon bucket. Pour in the hot melted soap mixture. Stir well, until all the powder is dissolved. Fill the bucket to the top with more hot tap water. Stir, cover securely, and let set overnight. The next morning, stir mixture. Mix equal amounts of soap concentrate and water in a smaller laundry detergent dispenser or container. Shake before using.

For top-loading machines: Use 1 cup of soap mixture per load.
For front-loading machines, use 1/3 cup per load

Note from Ann Kelly — I use my submersion blender after it has set for 24 hours and after I have stirred it well. This way I can put it in a bottle that has a “tap” I also do not dilute and just use less… because I don’t have the storage space.