Add oats to a high-speed blender and blend on high until a fine, powdery flour is achieved — about 15 seconds (it’s fast!). Be careful not to overblend or the oat flour will get clumpy.
Check your blender for bits of oats and continue blending, occasionally removing your blender from the base and shaking to ensure all oats are well blended.
Transfer to a jar or container and store up to 1 month unrefrigerated, often longer. See above for recipe suggestions.