In a medium bowl, whisk together oat flour, almond flour, salt, baking soda, cinnamon, nutmeg, ginger, and cloves. In a separate large bowl, mix together mashed banana, pumpkin, flax egg, vanilla, maple syrup, oil, and almond milk. Add dry ingredients to wet ingredients and mix until just combined. Do not overmix. Fold in mix-ins if desired. Evenly divide batter between muffin cups, filling about 2/3 of the way full.