Preheat oven to 350 degrees.
Make crumble topping:
Combine oats, flour, dark brown sugar, cinnamon, & nutmeg, in a medium bowl.
Cut in butter with a pastry blender until well combined and large crumbs form. Chill in the freezer until ready to use.
Make apple filling:
Whisk together sugar, corn starch, cinnamon, and salt in a large bowl. Add sliced apples and almond extract. Toss gently to combine.
Spoon apple filling into skillet and sprinkle evenly with crumble topping.
Bake crisp:
Place baking dish on preheated baking sheet and bake for 55 to 60 minutes, until golden brown and filling is bubbling. Mine only took 50 minutes.
Cool crisp on a wire rack for at least 30 minutes before serving.
Refrigerate leftover crisp tightly covered (or in an airtight container) up to 2 days.
You can make with other apples but I prefer the tartness of granny smith.
I also reduce the granulated sugar in the filling to 1/2 cup because I like it a tad more tart.