Using a cheese grater, shred your cold process soap using the fine grate option. If you have lye heavy soap, this is a great time to use it! If not, non-lye heavy soap works great too.
In a large mixing bowl, add the washing soda and citric acid. Washing soda can cause skin irritation, so I recommend wearing gloves and long sleeves when working with it. It can also irritate the nose and throat, so you can wear a mask if you like. Add the grated soap and mix to combine. Add the lavender 40/42 essential oil and use your hands or spatula to fully mix in. Spritz the mixture with rubbing alcohol until it has a slightly damp texture. This step is optional, but it helps the mixture keep its shape in the mold, much like a bath bomb!
As the laundry soap sits, it will begin to harden. You can place the soap into a jar, but within a few days it will harden and be difficult to scoop. To prevent this, I recommend placing it into individual cavity molds. I used the Small Cubes Mold & Package. In our tests, the Bendy Basics Molds worked great as well!