1. Preheat the oven to 350°F (175°C) and prepare an 8×8-inch baking pan by greasing with nonstick spray or lining with parchment paper.

2. If using whole rolled oats, pulse them 5-10 times in a blender for better texture (optional).

3. In a medium bowl, combine oats, flour, flaxseed (if using), cinnamon, pumpkin pie spice, baking powder, baking soda, and salt.

4. In a large bowl, whisk together eggs (or flax egg), pumpkin puree, maple syrup or sugar, melted coconut oil, and vanilla extract until smooth.

5. Stir the dry ingredients into the wet mixture until just combined, then fold in your chosen mix-ins.

6. Evenly spread the batter in the prepared pan and optionally press extra mix-ins on top.

7. Bake for 20-24 minutes or until lightly golden around edges and a toothpick comes out clean.

8. Cool in the pan before slicing into 16 squares.