Using a smoothie blender, add in spinach, almond milk, banana, eggs and vanilla. Blend until smoothie-like.
In a food processor, blend oats until fine (the more fine the fluffier the muffins will be). Add in salt, baking powder, baking soda, cinnamon, flax and sugar. Process until combined.
In a separate bowl, mix the dry and wet ingredients until no clumps.
Pour into lined muffins trays. This will easily fill 12.