1. Preheat your oven to 375 F (190 C). Lightly grease an 8×8-inch baking dish or a similar-sized oven-safe dish with cooking spray or a little butter to prevent sticking.

2. In a spacious mixing bowl, whisk together the rolled oats, protein powder, brown sugar, baking powder, ground cinnamon, and salt. Make sure everything is well combined so the baking powder is evenly distributed.

3. In another medium-sized bowl or a large measuring cup, whisk together the milk, maple syrup, melted coconut oil (or butter), and vanilla extract until smooth.

4. Pour the wet ingredients into the bowl with the dry ingredients. Stir gently with a spoon or spatula until just combined. Be careful not to overmix; a few lumps are fine.

5. Gently fold in the fresh or frozen blueberries and half of the sliced almonds into the batter. This ensures they are evenly distributed throughout the oatmeal.

6. Pour the oatmeal mixture into your prepared baking dish. Sprinkle the remaining sliced almonds evenly over the top of the mixture.

7. Place the baking dish in the preheated oven and bake for 30-35 minutes, or until the top is lightly golden brown and the oatmeal is set in the center. A knife inserted into the center should come out mostly clean.

8. Remove the baked oatmeal from the oven and let it cool for about 5-10 minutes before slicing and serving. This allows it to firm up slightly and makes for cleaner portions.