Preheat oven to 350°F. Grease a 9 ½ inch deep dish pie plate or 9x9 square baking dish. Set aside.
For the topping: combine flour, oats, brown sugar, salt, and cinnamon. Add melted butter and stir until combined. Set aside.
In a large bowl combine apples, juice, granulated sugar, flour, cinnamon, and vanilla. Stir gently until completely combined. Dump the mixture (and any accumulated juices) into the prepared baking dish. Using your fingers, crumble the mixture over the fruit, occasionally pressing some of it together to form clumps.
Spray a piece of foil with nonstick spray and loosely cover the baking dish. Bake 20 minutes. Remove the foil and bake for an additional 25-30 minutes, until the topping is golden brown, the apples are tender, and the juices are bubbling around the edges. Serve warm with vanilla ice cream.
You will need about 5-6 apples. Apples should be sliced ¼ inch thick or smaller. I recommend using Honeycrisp, Pink Lady, Fuji, or a combination of those.