Preheat the oven and pan. Preheat the oven to 350°F and line a loaf pan with parchment paper.
Prepare the flax mixture. In a small bowl, combine the flaxseed meal and water. Stir well and set aside for several minutes to bloom and thicken.
Mash the bananas. In a separate bowl, mash the bananas until mostly smooth. Stir in the lemon juice and set aside.
Mix the wet ingredients. In the bowl of a stand mixer fitted with the paddle attachment (or in a large bowl using a hand mixer), combine the melted coconut oil, sugar, and brown sugar. Mix until well combined.
Add the egg yolks. Add the egg yolks to the mixture and mix until fully incorporated.
Add remaining wet ingredients. Mix in the coconut milk, vanilla extract, and the bloomed flaxseed mixture until smooth.
Add the bananas. Stir the mashed banana and lemon juice mixture into the batter until evenly combined.
Add the dry ingredients. Add the gluten-free flour, baking powder, and baking soda. Mix just until combined, being careful not to overmix.
Fold in the chocolate chips. Toss the chocolate chips with a small amount of gluten-free flour, then gently fold them into the batter.
Rest the batter. Let the batter sit for 10–15 minutes so the gluten-free flour can fully hydrate. This helps improve the texture and structure of the finished loaf.
Transfer to the pan. Pour the batter into the prepared loaf pan and spread evenly.
Bake. Bake for about 1 hour, or until a toothpick inserted in the center comes out mostly clean with a few moist crumbs.
Cool before slicing. Allow the banana bread to cool in the pan for about 10–15 minutes, then transfer to a wire rack to cool completely before slicing.