If your shea butter isn't soft enough, you may need to melt it first. You can easily do this in the microwave for a few seconds or a double-boiler over the stovetop.
Combine shea butter, oil and essential oil(s) until you achieve a nice, creamy texture.
Add tapioca and bicarb soda to form a paste. If the deodorant seems a bit too soft or runny, place it in the fridge for a couple of hours to harden again.
Store deodorant in a small 60ml/2oz container in your bathroom cupboard or in the fridge, if you prefer.