Step 1: Preheat your oven to 350°F (175°C) and line an 8x8 inch square baking pan with parchment paper for easy removal.
Step 2: In a large bowl, whisk together the rolled oats, almond flour, and sea salt until well combined.
Step 3: Add the melted coconut oil and maple syrup to the dry ingredients. Stir until the mixture is evenly moistened and starts to clump together.
Step 4: Press two-thirds of the oat mixture firmly into the bottom of the prepared baking pan to form the bottom crust.
Step 5: Bake the bottom crust for 10 minutes, then remove from the oven and set aside.
Step 6: In a medium bowl, gently toss the blueberries with lemon juice, lemon zest, and arrowroot powder until the berries are coated.
Step 7: Spread the blueberry mixture evenly over the par-baked crust.
Step 8: Sprinkle the remaining one-third of the oat mixture over the blueberries, pressing down slightly.
Step 9: Bake for an additional 20-25 minutes, or until the topping is golden brown and the blueberry filling is bubbling.
Step 10: Allow the bars to cool completely in the pan on a wire rack, then refrigerate for at least 2 hours before slicing into 9 squares.