Chop the block of soap into small chunks. Place in a ceramic bowl and microwave in 15 second intervals until completely melted (about 45 seconds).
Add 15-20 drops of essential oil and use a wire whisk to mix it all together.
If you’re using metal molds, lightly coat them in non-stick cooking spray and wipe out the excess. Pour the soap into the molds and let cool to room temperature.
Remove the soap from the molds and sprinkle with herbs (if you need help releasing the soap from the molds, pop them in the freezer for 10 minutes). Stack two or three soaps together and tie them with kitchen twine.