By helen from U.K
Oat flour is just like wheat flour, oats that are ground up. Use your food processor or blender (if using blender, do only a small amount at a time) to grind it up. It's just that simple and probably cheaper than buying it at a health food store.
It is ground up oatmeal. Just put about a cup of oatmeal in a blender or food processor and process until of flour consistency. Store in an air tight container.
You could try a natural grocery store, or, if you want to be thrifty, you can take regular oats for oatmeal, and grind them up in a blender or food processor!