Preheat the oven to 350 degrees Fahrenheit.
Add the coconut flour, ground flaxseed, and baking soda to a mixing bowl, then mix well.
Add the bananas to a mixing bowl and use a potato masher or fork to mash them.
Add the unsweetened almond milk, maple syrup, almond butter, apple cider vinegar, vanilla extract, cinnamon, nutmeg, and salt to the mixing bowl with the bananas, then use a whisk to mix well.
Add the dry ingredients to the wet ingredients, then use a spoon to mix until combined (the batter will be very thick).
Transfer the batter to a 9-inch loaf pan lined with parchment paper.
Use a spatula or the back of the spoon to smooth the batter evenly in the pan.
Bake for 50 minutes or until a toothpick inserted into the center of the loaf looks clean upon removal.
Let the banana bread cool to room temperature before removing from the pan and serving.