Preheat the oven to 350°F.
In a large bowl, mix together blueberries, raspberries, maple syrup, lemon juice, and vanilla extract.
Then add tapioca flour or cornstarch and toss blueberries.
Spoon berries into an 8×8 inch pan, letting the berry juice drain in the bowl.
In another bowl, mix together oats, walnuts, oat flour, and salt.
Stir in maple syrup, coconut oil, and vanilla until well combined.
Spread cobbler topping on top of blueberries until most of the blueberries are covered.
Bake in oven for 40-45 minutes or until topping is golden brown.
Let cool for 15 minutes before eating. Store leftovers in refrigerator.