Oil an 8 x 8 baking dish and preheat the oven to 350F.
Mix the oats, salt, cinnamon, ginger, and flax together in a large mixing bowl. Fold in the frozen berries. banana, and walnuts.
Blend together the almond milk, remaining banana, and sweetener. Pour the liquid over the dry ingredients and mix well. Transfer the whole mixture to the baking pan.
Bake the oats for 40-45 minutes, or until the top is browning and firm. Allow the oats to set for at least thirty minutes before cutting into servings and enjoying.