Preheat the oven to 350 degrees Celsius. Line an 8x8 pan with parchment paper.
In a medium bowl, combine oats, oat flour, almond flour, coconut, baking powder, cinnamon, nutmeg and salt. Stir together.
With a hand-held or stand mixer, cream the softened coconut oil and sugar together in a large bowl. Once combined, add the maple syrup, almond butter, egg and vanilla extract.
Add the dry ingredients to the wet and fold everything together.
Add the chopped apple and stir once more. Add the water to moisten it.
Place the batter into the lined pan. Sprinkle the top with chopped walnuts (optional).
Bake for 30-40 minutes, or until an inserted toothpick comes out clean.
Let the bar cool for 10-20 minutes before cutting into it. This will prevent it from crumbling.
Keep the bar in the fridge for 1 week or store in the freezer for 1-2 months.
Notes
*To make oat flour, simply blend up oats in a blender until it becomes a fine powder.