Preheat the oven to 375° F.
In a small bowl, mix together the ground flaxseed and water. Set the mixture aside for about five minutes to form a flax "egg".
Add the oat flour, almond flour, baking soda, and cinnamon to a large mixing bowl and mix until all ingredients are well combined.
Mash the bananas with a fork, then add them to the center of the mixing bowl along with the flax "egg", nut milk, and vanilla extract.
Mix all wet ingredients together, then slowly mix the wet into the dry to form a smooth muffin batter.
Gently fold in the blueberries.
Evenly distribute the batter between six cavities of a lined or greased muffin pan.
Bake the muffins for about 20 minutes, or until a toothpick inserted comes out clean.
Let the muffins cool for a bit.
Dig in and enjoy your muffins with whatever toppings you'd like (I added peanut butter on top of mine).