Chop up the melt and pour soap base into small, equal sized squares.
Place the squares in a large mason jar or glass jug.
Heat on high in the microwave for 30 seconds. When done, remove and stir.
Continue heating for 30 second intervals, stirring between each interval, until the soap base is melted. This process can also be done in a double boiler.
Once melted, add the hibiscus powder and stir until combined.
Let the mixture cool slightly, then add the essential oils if using and mix through.
Pour the soap into the soap mould.
Set aside for the soap to set until hard. This can take a few hours, though it is better to leave them set overnight.