Making Vegan Berry Crumble Bars is as simple as following these straightforward steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Line an 8×8 inch baking dish with parchment paper for easy removal.

2. Combine Dry Ingredients: In a large mixing bowl, combine rolled oats, almond flour, cinnamon, and salt, stirring until evenly mixed.

3. Mix Wet Ingredients: In another bowl, whisk together melted coconut oil, maple syrup, and vanilla extract until well combined.

4. Combine Mixtures: Pour the wet mixture into the dry ingredients, stirring until just combined. The mixture should be crumbly but hold together when pressed.

5. Prepare Berry Filling: In a small bowl, toss the mixed berries with cornstarch (if using) to coat them. This will help thicken the juices while baking.

6. Layer the Mixture: Press half of the oat mixture firmly into the bottom of the prepared baking dish to form a crust layer.

7. Add Berries: Evenly distribute the mixed berries over the crust, ensuring they are spread out for maximum flavor in every bite.

8. Top with Crumble: Sprinkle the remaining oat mixture evenly over the berries, ensuring a good coverage.

9. Bake: Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and crisp.

10. Cool Down: Once baked, remove from the oven and allow the bars to cool in the pan for about 10 minutes. Then, lift them out using the parchment paper for easier cutting.