Preheat oven to 350°F (175°C) and lightly grease a 9x5-inch loaf pan.
In a large bowl, whisk together the oat flour, baking soda, salt, and cinnamon.
In a medium bowl, combine the mashed bananas, eggs, melted coconut oil, maple syrup, and vanilla extract.
Pour the wet mixture into the dry ingredients and stir until just incorporated.
Fold in the chopped walnuts.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake for 45 to 55 minutes, or until a wooden skewer inserted into the center comes out clean.
Cool the bread in the pan for 10 minutes before transferring to a wire rack to cool completely.