Mix the oat milk with the flax seeds in a small bowl and rest for 10 minutes.
Put everything in a blender and whiz until you get a thick but pourable mixture. Add more milk if the mixture is too thick.
Heat your waffle maker, then spray the plates with oil.
Spoon some batter into the waffle maker, spreading it out evenly. Close the top and cook for 3-5 minutes (depending on your machine). When the waffle is golden, move to a plate and repeat. You should be able to make about 4-6 waffles, depending on your maker.
Serve warm with your chosen toppings.