If your coconut oil isn't liquid, melt it in the microwave or over the stovetop.
In a bowl (wood, plastic or glass) mix clay, charcoal, and xylitol (if using) with a spoon or spatula (also, wood, plastic, glass or silicone).
Now add liquid coconut oil. Add your preferred amount of drops of essential oil to one of the tablespoons of coconut oil before mixing it in.
Mix until everything is well incorporated and no lumps are left. If the toothpaste seems too crumbly, add more oil. If too runny, add more clay.
Store in a 60ml / 2oz container. A little glass jar works best.