Preheat the oven to 375°F.
Lightly grease a pie dish (or 8x8-inch baking dish).
In a large bowl, toss berries with arrowroot starch, lemon juice, maple syrup, and vanilla. Pour the mixture evenly into the prepared dish.
In a medium bowl, whisk together the almond flour, oat flour, coconut sugar, baking powder, and salt.
In a separate small bowl, whisk the egg. Add the coconut oil (or melted ghee), maple syrup, and vanilla extract, whisking until smooth.
Combine the wet mixture and the dry ingredients and stir until a thick, slightly sticky dough forms.
Using a spoon or cookie scoop, drop the dough in mounds (about 2–3 tablespoons each) over the berry mixture. Lightly flatten the tops with the back of your spoon so they spread a bit while baking, leaving small gaps for the juices to bubble through.
Bake 25–35 minutes, until the topping is golden brown and the berries are bubbling around the edges.Note: If the topping is browning quickly, loosely tent with foil for the last 5–10 minutes. Cool for at least 10–15 minutes to let the filling set before serving. The topping will be crisp on the outside and tender inside, with a jammy berry base. Option to add scoops of vanilla ice cream on top (keep it dairy-free, if needed!) to serve. Enjoy!