Preheat the oven to 350 F. Grease a 9x5 inch loaf pan or line it with parchment paper.
Prepare the flax egg: In a small bowl, mix the ground flax seeds and 3 tablespoons warm water. Let this sit for a few minutes while you prepare the wet ingredients.
Mix the wet ingredients: In a large bowl, add all of the wet ingredients (including the flax egg) and whisk until smooth.
Mix the dry ingredients: In a separate bowl, add all dry ingredients except for the chocolate chips and whisk to combine.
Combine all ingredients: Pour the dry ingredients into the wet ingredients stirring gently until just combined. Make sure to not over-mix the batter to avoid a gummy texture. Fold in the chocolate chips.
Bake: Pour the batter into the prepared loaf pan. Set a timer for 30 minutes. After the initial 30 minutes, tent the loaf with foil and bake for an additional 20-30 minutes, or until a toothpick inserted into the center of the loaf comes out clean.
Cool and serve: Let the loaf pan cool for 10 minutes before removing the loaf. Transfer to a wire rack to completely cool before slicing. Slice into 10 even pieces. Store any leftovers in an airtight container or wrap with plastic wrap and store in the fridge.
Notes
The foil tent helps to prevent the outside of the loaf from getting too brown before the inside is cooked all the way.
You can make your own oat flour by grinding rolled oats in a coffee or herb grinder.
You can also grind your own whole chia seeds and flax seeds in a coffee or herb grinder.
All ingredients are naturally gluten-free. However, if you are celiac or very sensitive to gluten, make sure to double check that all the brands you choose are tested for gluten.