Combine oats, baking powder, salt and flax seed in blender and process until it becomes flour.
Combine water and vanilla in large batter bowl. Add flour to water and whisk until just combined.
Preheat waffle iron and allow batter to thicken for about 5 minutes. Add additional water to thin to desired consistency.
You may wish to cook one small waffle and see if they will release from your waffle iron without greasing it. Thinner batter does result in fluffier waffles but they also stick a little more easily.
Cook for about 4 minutes or until they reach desired crispiness.