Preheat the oven to 375°F.
In an 8-by-8-inch baking dish, mix together 2 cups of oats, the plant-based milk, 2 tablespoons of maple syrup, the cinnamon, apple, vanilla, flaxseeds, and 1 cup of water.
In a blender, pulse the macadamia nuts to a meal-like texture.
In a medium bowl, mix together the whole-wheat flour, macadamia nuts, the remaining ¼ cup of oats, remaining 2 tablespoons maple syrup, and 3 tablespoons water to form a loose dough. Crumble the mixture over the top of the oatmeal mixture.
Bake for 35 minutes, or until the top is crispy. Let cool for 10 minutes to set, then cut into 4 squares. Refrigerate for up to 4 days.
