01 - Set the oven to 350°F (180°C) to preheat.
02 - In a large bowl, combine sliced apples with lemon juice, granulated sugar, cinnamon, nutmeg, and flour. Mix thoroughly and transfer to a greased 9-inch (23 cm) baking dish.
03 - In a separate bowl, blend flour, diced butter, brown sugar, oats, and salt. Rub with fingertips until mixture forms coarse crumbs.
04 - Evenly distribute the crumble topping over the apple mixture in the baking dish.
05 - Bake for 35 to 40 minutes, or until the topping is golden brown and the filling is bubbling.
06 - Allow to cool slightly before serving warm. Optionally accompany with vanilla ice cream or custard.