Preheat the oven to 350°F (180°C) fan.
Make the flax egg by combining the ground flaxseeds with water. Let it sit for 5 minutes.
If your coconut oil is solid, you can melt it in the microwave on defrost function at 15 second-intervals. This allows the coconut to melt without getting too hot.
Grate 2-3 organic lemons using a zester. Juice the lemons until you obtain ½ cup of juice.
In a large mixing bowl, whisk the oat flour with the almond flour, arrowroot powder and baking soda.
Form a well in the center of the ingredients and add in the flax eggs, melted coconut oil, sugar, lemon zests and lemon juice. Start whisking at the center and gradually incorporate flour from the sides until combined. Stir in the poppy seeds but don't overmix the batter.
Line a muffin pan with 6 muffin liners. Fill each cup up to the top with 3-4 tablespoons of batter.
Bake the muffins for 22 minutes or until a tester comes out clean. The tops should be golden.
Let the muffins cool down completely. The texture improves a lot while they cool down.