PREP: Position a rack in the center of the oven and preheat the oven to 350ºF. Spray a 9x13 baking dish or a 10-12 inch cast iron skillet with nonstick cooking spray. Set this aside for now.
FILLING: in a large bowl, combine the apples slices with lemon juice, brown sugar, vanilla bean paste, cinnamon, kosher alt, and cornstarch. Toss to coat the apple slices. Add the apple filling to the prepared dish or skillet, set aside for now.
CRUMB TOPPING: in a medium bowl, toss together the ingredients for the oat topping. Add the rolled oats, light brown sugar, flour, and cinnamon. Mix using a whisk or with your hands.Add the cubed butter and break it down using pastry blender or with your fingertips. Some kidney bean-sized pieces are okay. Sprinkle the oat crumble mixture over the apple slices.
BAKE: place the apple crisp in the oven and let bake for 35-45minutes or until the filling is bubbly and the oat topping is golden brown. If at any point the filling starts to brown too much, loosely tent with a piece of foil.
LET COOL: once done, allow the apple crisp to cool for 10 minutes before serving topped with vanilla ice cream scoops and salted caramel sauce. Enjoy!