Herbal soaps take a glycerin soap base mixed with herbs and essential oils or dried fruits. You also need a double boiler, a rubber scraper, molds for the soap and either cooking spray or petroleum jelly.
The first step is to coat the soap molds with cooking spray or petroleum jelly and set them aside. Next, chop the glycerin soap base into even pieces, approximately half inch chunks. Melt in the double boiler, stirring frequently with the rubber scraper. The base should become liquid but shouldn't boil. Add whatever herbs or scents and pour into molds. For even distribution, allow soap to cool slightly before pouring in the herbs. After soaps have set for 60 minutes, transfer to the freezer until they harden.
Dried herbs such as lavender and rosemary work well. Steep the herbs in an infusion to add to the soap, discarding the solids. Save a few decorative pieces for the tops of soaps. Essential oils add scent without solids. Use between half teaspoon to two teaspoons per three cups of glycerin soap base, depending on the desired strength of the soap. Another option is to use fresh herbs. Puree these in a food processor with one to two tablespoons of water. Wring out excess water in a coffee filter. If without soap molds, use clean containers from yogurt, juice concentrate or milk cartons and slice the soaps once hardened.