Preheat your oven to 325°F. While it heats, line an 8x8-inch baking dish (or similar size) with parchment paper, allowing the paper to overhang the sides slightly—this makes it easier to lift the bars out after baking and cooling. Set the prepared pan aside.
In a large bowl, combine the finely chopped nuts, oats, 1/3 cup blueberries, flaxseed, salt, and cinnamon. Stir everything together until evenly distributed. The finely chopped nuts are crucial here—they help bind the bars together better than larger pieces would, creating a more cohesive texture.
In a separate bowl, whisk together the melted and cooled coconut oil, creamy almond butter, maple syrup, and sugar until well combined and smooth. The almond butter acts as a binding agent, so make sure it's fully incorporated with no lumps remaining.
Pour the wet mixture from Step 3 into the dry ingredients from Step 2 and stir vigorously until everything is evenly coated and holds together when squeezed. Transfer the mixture to your prepared pan and press it firmly and evenly into all corners using the back of a spatula or your hands. I like to use a measuring cup or small glass to press down with consistent pressure—this helps create an even texture and prevents crumbling later. If using the optional 1 tablespoon of blueberries for topping, press them firmly into the surface now.
Bake in the preheated 325°F oven for 22-27 minutes, until the surface is light golden brown. The bars should feel set to the touch but still have a slight give when gently pressed in the center. Remove from the oven and let cool in the pan for 30 minutes—this is important because the bars will continue to set as they cool and will be easier to slice.
After 30 minutes in the pan, lift the bars out using the parchment paper overhang and transfer them to a wire cooling rack. Allow them to cool for another 1-2 hours until completely set and at room temperature. Once cooled completely, cut into 12-16 bars using a sharp knife, wiping the blade between cuts for clean edges. Store in an airtight container for up to 5 days.