Preheat your oven to 350°F (175°C) and line an 8-inch square baking dish with parchment paper.

In a large mixing bowl, combine the oats, almond flour, maple syrup, coconut oil, vanilla extract, baking powder, and salt. Mix until well combined.

Set aside 1 cup of the oat mixture for later, then press the remaining mixture firmly into the bottom of the prepared baking dish.

In a separate bowl, toss the mixed berries with cornstarch and lemon juice until evenly coated.

Spread the berry mixture over the crust in the baking dish, distributing evenly.

Crumble the reserved oat mixture over the berry layer.

Bake in the preheated oven for 30 to 35 minutes until golden brown and bubbly.

Allow the bars to cool, then lift out using the parchment and slice into squares.