Prepare the Filling: In a mixing bowl, combine the fresh blueberries, honey or maple syrup, lemon juice, and cornstarch. Stir gently to coat the blueberries evenly. Transfer the blueberry mixture to the baking dish, spreading it out evenly.
Make the Crumble Topping: In another bowl, mix together the rolled oats, almond flour, chopped nuts, melted coconut oil, honey or maple syrup, cinnamon, and salt until well combined.
Assemble: Sprinkle the crumble topping evenly over the blueberry mixture in the baking dish.
Bake: Place the baking dish in the preheated oven and bake for 30-35 minutes, or until the topping is golden brown and the blueberries are bubbling.
Cool and Serve: Allow the crumble to cool for a few minutes before serving. Enjoy warm with a dollop of Greek yogurt or on its own.