Step 1: Cut up 1/2 cup of clear soap and melt it for 15-20 seconds in the microwave. Stir and microwave again if needed to just melt the soap but don’t let it boil. Add your colorant (I used a tiny sliver of a solid block colorant, but a few drops of liquid colorant also works), and stir to combine.
Step 2: Tip your mold up using a slim book on each end, and pour your soap into 1 side of each rectangle mold until it reaches about 3/4 of the way to other side. Now spray rubbing alcohol to get rid of any air bubbles and smooth out soap. Repeat the rest of your soap and mould cavities. Let soap cool for 20 mins.