Preheat the oven to 350F. Lightly grease an 8-inch pie plate or a cast-iron skillet.
In a large bowl, toss together the blueberries, vanilla, lemon juice, arrowroot powder for thickening and salt until well coated.
Transfer the filling to the prepared pie plate.
Chop the butter into small pieces and add to the bowl with the oats, coconut sugar, almond flour, vanilla, salt, and lavender.
Pinch it all together with your fingertips until it forms a shaggy, sandy dough.
Sprinkle the topping evenly over the filling.
Layer the topping on the filling and bake for 45 minutes or until the filling bubbles and the topping is golden brown.
Allow to cool for at least 15 minutes.