Whisk the corn starch and baking soda together, then add coconut oil a little at a time until you get the consistency you want. It should look like standard store-bought deodorant. Pack it into a container. This fills a 4-ounce jar to the brim.
To use: Scoop a small amount up with your fingertips and rub it in. I find it works best immediately after showering, and letting it “soak in” a bit before getting dressed.