Preheat the oven to 350°F. Lightly spray a 9x5-inch loaf pan with oil and set aside.In a large bowl, mash the banana until almost smooth.Stir the wet ingredients (ground flax, milk, melted oil, maple syrup, and vanilla) into the banana until combined.Stir the dry ingredients (sugar, oats, baking soda, baking powder, salt, and flour) into the wet mixture, one by one, in the order listed. Stop stirring when there are no flour patches at the bottom of the bowl.Spoon the dough into the loaf pan and spread out evenly. Sprinkle the chopped walnuts over the batter and slightly press them into the batter to keep them from falling off once the bread is cooked.Bake the loaf, uncovered, for 45 minutes, until lightly golden and firm on top. The top of the loaf should slowly spring back when touched.Place the loaf pan on a cooling rack for 30 minutes. Then, remove the bread from the pan and let it completely cool before slicing. Or not ??