Oat flour comes across as an exotic ingredient in a recipe until you realize that all it is, is oats. Ground. And that it is so simple to make it will have you craving oaty goodness! If you poke around the interwebs you will see many sites on how to grind the oats. After trying out a couple of methods I can say this:
Don’t waste your time with a blender. My feeling is it is recommended as most houses have one, where as a food processor or well powered mini-food chopper isn’t as common. The blender was frustrating, slow to grind and leaving uneven chunks. Instead I pulled out my mini chopper and processed about 1 cup oats at a time and had gorgeous flour quickly. The sharp blade cut right through.
With large batches a food processor works quickly. But the beauty of oat flour is you can make just what you need, right before you need it. And it keeps it fresher when it stays as oats until it is needed.
Do grind a bit more oats, a cup of old-fashioned oats will produce about 6 to 7 Tbsp worth of flour (or about 7/8ths of a cup).
Producing a rustic flour: