If you are using a combination of liquids like water and witch hazel, mix them together now. Remember that if you have sensitive skin, you can neutralize the clay somewhat by using witch hazel, apple cider vinegar, or aloe juice to lower the pH as needed. If using only water, the pH of the mask will be higher, which can be irritating to some people's skin.
Mix together the bentonite clay and the activated charcoal using plastic or wooden silverware. (Don't use a metal bowl.)
Add the clay mixture to the liquid mixture, and allow the clay to absorb the liquid little by little.
Stir together all of the ingredients, mixing them until they are well combined.
You can now apply the facial mask by spreading a thin layer of the mask all over the face, leaving the area around your eyes and your lips uncovered.
Allow the mask to completely dry.
Rinse the mask off completely with cool water and gently pat your skin dry.
Notes
The amounts listed will make enough for several batches. I recommend mixing up the dry ingredients and storing them for later. (You could incorporate the essential oils into your dry ingredients to make future mixing easier.)Then take a small amount of the clay mixture (1-2 teaspoons) and mix it with a small amount of witch hazel when you are ready to use the mask.