*I used Kosher salt - actually flat salt crystals and they will dissolve quicker in a lower temperature water.
Mix together the soap, oil, and food coloring if desired. Pour this mixture over the rock salt in a large plastic or glass bow. Stir continuously until the salt crystals are evenly coated. Spread the salts out in a thin layer on a cookie sheet covered with wax paper and allow to air dry. Drying can take up to 24 hours depending on the depth of salts, humidity in your area and other factors. Put the bath salts into a decorative container when they are completely dry.
Consider adding a pouf or loufa sponge by simply hooking the rope around the jar. Another easy option for presentation of this jar is to include it in a basket of relaxation and spa time products such as a book, candle, and lotion.