Combine dry ingredients (flours through salt) together in a large bowl. (I usually use my mixer.) Add oil or butter. If using butter, grate the butter first. If using coconut oil or shortening, dump it in at one time. If using a liquid oil, drizzle it in while stirring or running the mixer.
Mix until combined. Store in the refrigerator or freezer if using butter. Otherwise it is shelf stable for about a month or you can store it in the freezer for longer.
Butter is the most difficult to incorporate into the baking mix. You can use any combination of oil or oils that you choose. If you wish to make a shelf stable mixture, use all white flour and use shortening in place of the oil or butter.
Homemade Baking Mix https://www.dogwoodsanddandelions.com/homemade-baking-mix/