Prepare Apples: Preheat your oven to 375°F (190°C). In a large bowl, combine the sliced apples, granulated sugar, 1 tablespoon of flour, 1 teaspoon of cinnamon, nutmeg, and lemon juice. Toss gently until the apples are evenly coated. Pour the apple mixture into an 8x8 inch or 9x13 inch baking dish, spreading them evenly.
Make the Topping: In a separate medium bowl, whisk together 1 cup of flour, brown sugar, rolled oats, 1/2 teaspoon of cinnamon, and salt. Add the cold, cubed butter to the dry ingredients. Use your fingertips, a pastry blender, or a fork to cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining.
Assemble and Bake: Evenly sprinkle the crisp topping over the apple mixture in the baking dish. Place the baking dish on a baking sheet to catch any potential drips. Bake for 35-45 minutes, or until the topping is golden brown and the apples are tender and bubbling. If the topping browns too quickly, you can loosely tent it with aluminum foil.
Cool and Serve: Remove the apple crisp from the oven and let it cool for at least 15-20 minutes before serving. This allows the filling to set slightly, preventing it from being too runny. Serve warm, perhaps with a scoop of vanilla ice cream or a dollop of whipped cream.