Mix chia seeds and water together in a small bowl; set aside.
Add oats to a blender and blend until a flour-like consistency is formed. Add to a bowl along with the coconut flour, coconut flakes, baking powder, cinnamon, and salt. Mix well.
Heat coconut oil just until melted, then add to a small mixing bowl. Whisk in vanilla, maple syrup, coconut milk, and the chia mixture. Gradually add this to the dry ingredients. Allow to sit for 1 minute.
Following your waffle iron's manufacturing instructions, cook waffles in batches until all the batter has been used.
Top with remaining maple syrup. Serve sliced mango on the side.