Lightly crush the herbs. Gently bruise the herbs using a pestle and mortar, spice grinder, or even your hands. You don’t need a powder—just break up larger pieces so they infuse better.
Add the herbs to a jar. Place the crushed herbs in a clean, heatproof glass jar or container.
Pour in the oils. Add olive, jojoba, and castor oils over the herbs. Stir or poke with a spoon to make sure all the herbs are fully submerged. Add a little extra oil if needed.
Infuse with gentle heat. Screw the lid on and place the jar in a small saucepan with a folded tea towel underneath. Fill the pan with water halfway up the jar. Heat on very low for 2–4 hours, keeping the oil warm but never hot.
Strain the herbs. Pour the oil through a fine-mesh sieve into a clean jar or cup. For a clearer oil, line the sieve with cheesecloth. Press the herbs gently with a spoon and let them sit in the sieve for 30 minutes to release all remaining oil.
Transfer and store. Stir in the vitamin E oil and the essential oils (if using). Pour the oil into a small dark glass jar or dropper bottle. A dropper bottle makes it easy to apply just a few drops per use, keeping your DIY hair and scalp oil mess-free.