Put 1 3/4 cup of gluten-free whole oats into a blender and blend for about 1 minute until the oats have turned into flour.
Pour into a wire mesh strainer or a flour sifter and sift over a large bowl until all the fine flour has fallen through. (Throw away the large pieces of bran that are left in the strainer).
Add tapioca flour, xanthan gum, baking powder, and salt to the oat flour and then give it a good stir.
If you wish to add the shortening, add all of the dry ingredients along with 2 tbsp of shortening to a food processor and blend until it's all incorporated.
Store in an airtight container for up to 3 months and use it as you would Bisquick.
Notes
Notes:
I have noticed that recipes occasionally require slightly more liquid when using this gluten-free Bisquick, if you use homemade oat flour vs the storebought flour.
The homemade oat flour tens to have more bran than the store bought oat flour and works better if you measure by weight rather than volume.
Make sure to mix it up well so you have the proportions evenly distributed within the mix.
You can leave out the shortening to make it fat-free.