Step 1: Preheat your oven to 375°F (190°C). Lightly butter a 9x13 inch baking dish.nStep 2: In a large bowl, combine the sliced apples, granulated sugar, 1/4 cup brown sugar, 1 tablespoon flour, 1 teaspoon cinnamon, nutmeg, and lemon juice. Toss gently until the apples are evenly coated. Pour the apple mixture into the prepared baking dish and spread evenly.nStep 3: To make the topping, in a separate medium bowl, combine 1 cup flour, rolled oats, 1/2 cup brown sugar, 1/2 teaspoon cinnamon, and salt. Mix well.nStep 4: Add the cold, cubed butter to the dry topping ingredients. Use your fingertips, a pastry blender, or a fork to cut the butter into the mixture until coarse crumbs form and the butter is evenly distributed. Some larger clumps are desirable for a crispier topping.nStep 5: Evenly sprinkle the crumble topping over the apple mixture in the baking dish.nStep 6: Bake for 45-55 minutes, or until the topping is golden brown and the apple filling is bubbly and tender when pierced with a fork. If the topping browns too quickly, you can lightly tent it with aluminum foil.nStep 7: Remove from the oven and let it cool for at least 15-20 minutes before serving. This allows the filling to set slightly. Serve warm, preferably with a scoop of vanilla ice cream or a dollop of whipped cream.