Add 1-3 cups of oats to the blender. Secure the lid.
Start on low and increase the speed. Run for about 30 seconds. If making a larger quantity you may need to run it longer.
Food Processor
Add 1-5 cups of oats to the food processor. Secure the lid.
Run the food processor for about 1 minute. You make need to pulse it too. If making a larger quantity you may need to run it longer.
Immersion Blender
Add 1 cup of oats to a tall cup.
Use the immersion blender to run through the oats. You may need to use a spoon to move the oats around and then use your immersion blender again. It should take about 3 minutes.
Notes
Tips:
Results will vary based on your model of kitchen appliance.
As the appliances run the oat flour will begin to heat up from the friction and the machines. This will cause it to look a little clumpy. Once it cools it will be nice and floury.