Weigh all ingredients using a digital scale.
Add soy wax, cocoa butter, and shea butter to a heat-safe container.
Melt using a double boiler until fully liquid (around 160–170°F).
Remove from heat and stir in castor oil.
Allow the mixture to cool to 140–145°F, then add fragrance oil.
Stir gently for 1–2 minutes.
Pour into a heat-safe candle jar with a properly sized wick.