Set up your workspace. I like to line a cookie sheet with parchment or wax paper and set all of the lip balm tubes huddled together, lids off. This makes it easier to pour the lip balm mixture into the containers quickly.
Heat about 2 cups of water in the bottom of a double boiler on medium to medium-high heat. (You can make your own double boiler by adding water to a saucepan and putting a glass bowl, mason jar, or wax melting pitcher (that's what I use) into the water.
Add coconut oil, beeswax, and cocoa butter to the top part of the double boiler and heat until melted. Use a wooden skewer or popsicle stick to stir.
After it's melted, remove double boiler from heat and add the peppermint oil, stirring to combine.
Pour lip balm mixture quickly into lip balm containers. It starts to harden quickly, so you need to work fast.
Usually the lip balm mixture will sink down a bit in the center. If this happens, simply pour more on top until it's even with the top of the lip balm tube.
Allow to cool at room temperature and harden fully, then add lids to the containers.
Notes
If you'd like to add other ingredients, like castor oil, here's the ingredient list I use for that (the instructions are the same as above) to make 12 lip balm tubes:2 1/2 tbsp. coconut oil1/2 tbsp castor oil1 tbsp beeswax1 tbsp cocoa butter15 drops peppermint essential oilThis makes a slightly less-firm lip balm than just using the above ingredients.