Set the oven to 350°F and line or grease a 12-cup muffin tin.
Combine the ground flax seeds and water in a medium bowl. Stir and allow it to rest for 5 minutes.
Add the bananas, avocado oil, maple syrup, and vanilla to the flax seed mixture. Use a fork to mash the bananas.
In another bowl, combine the almond flour, all-purpose flour, baking soda, cinnamon, and salt. Stir thoroughly.
Mix the wet ingredients with the dry ingredients and stir until just combined, being careful not to over mix.
Fold in the chopped apple and combine.
Divide the batter into the muffin tin and bake for 35 minutes,
Once done, let cool until transferring the muffins to a glass container for storage.