Preheat the oven to 350°F and grease or line an 8×4-inch loaf pan with parchment paper.
In a large mixing bowl, whisk together 2 1/4 cups blanched almond flour, 1/4 cup arrowroot flour (or cornstarch), 1/4 cup ground flaxseed, 1/4 cup coconut sugar (or light brown sugar), 1 tsp baking soda, 1/2 tsp ground cinnamon, and 1/4 tsp sea salt until well combined.
In another mixing bowl, mash 3 medium very ripe bananas (about 1 1/4 cup mashed). Stir in 2 tbsp avocado oil (or other neutral oil) and 1 1/2 tsp vanilla extract until combined.
Pour the wet mixture into the dry ingredients and stir until just combined.
Fold 1/2 cup chopped walnuts or pecans and 1/2 cup vegan chocolate chips into the batter.
Pour the batter into the prepared loaf pan and spread it evenly with a spatula or spoon.
Thinly slice one ripe yellow banana (not overripe) and arrange the slices on top of the batter to create a split-banana topping.
Bake the bread 40-45 minutes or until a toothpick inserted comes out clean and the loaf is golden brown.
Transfer the pan to a wire cooling rack and allow the loaf to cool at room temperature for about 30 minutes or until cooled through. For quicker cooling, lift the loaf from the pan using the parchment and cool directly on the rack.