It's really easy to make homemade oat flour! I use this for a few recipes, cookies, pancakes, and have a hard time finding an organic, gluten-free flour, so I make my own! It can be made using two different types of oats.
Use either steel-cut or oat flakes.
Add oats to a high-speed blender.
Blend for several minutes until you have a fine flour.
Store the oat flour in an airtight container or use it immediately in a recipe.
I use up my freshly made oat flour within a few days.