Preheat and prep: Heat your oven to 350°F (175°C). Lightly grease a 9-inch square baking dish or similar 2-quart dish.

Mix the berry filling: In a large bowl, combine berries, maple syrup or sugar, cornstarch, lemon juice, lemon zest, vanilla, and a pinch of salt. Gently toss until the berries are evenly coated and the starch dissolves. Pour into the prepared baking dish and spread into an even layer.

Make the crumble: In another bowl, stir together oats, almond flour, gluten free flour, brown sugar, cinnamon, nutmeg, and salt. Add the cold butter cubes. Use your fingers or a pastry cutter to work the butter into the dry mix until it forms coarse crumbs with some pea-size bits. Stir in vanilla and nuts or seeds if using.

Top the berries: Sprinkle the crumble evenly over the berry mixture. Don’t pack it down—those peaks and valleys get extra crispy.

Bake: Place the dish on a baking sheet to catch drips. Bake for 35–45 minutes, until the topping is golden brown and the berry juices are bubbling around the edges.

Cool slightly: Let the crumble rest for at least 15 minutes. This helps the juices thicken so the filling isn’t runny.

Serve: Spoon into bowls and add ice cream, whipped cream, or yogurt. Enjoy warm.