Preheat the oven:
Preheat your oven to 350°F (175°C). Grease an 8x8-inch baking dish lightly with butter or non-stick spray.
Prepare the filling:
Spread the canned apple pie filling evenly across the bottom of the prepared baking dish. Sprinkle 1/2 tsp of ground cinnamon over the filling if you want extra spice.
Make the topping:
In a mixing bowl, combine the flour, oats, brown sugar, granulated sugar, cinnamon, nutmeg (if using), and salt. Stir to mix. Add the melted butter and stir until the mixture resembles coarse crumbs.
Assemble the crisp:
Evenly sprinkle the oat topping over the apple filling, covering it completely.
Bake:
Bake in the preheated oven for 35–40 minutes, or until the topping is golden brown and the filling is bubbling around the edges.
Cool and serve:
Let the apple crisp cool for about 10 minutes before serving. Serve warm with a scoop of vanilla ice cream or a dollop of whipped cream for the perfect finishing touch.