Preheat oven to 350ºF. Add berries, sugar, arrowroot powder and lemon juice to a small ovenproof bowl and mix until berries are evenly coated. Set aside.
Add melted vegan butter or coconut oil to a separate small bowl and mix in sugar, almond flour and oats. Sprinkle on top of berry mixture and bake for 35-40 mins. Let cool and enjoy.