01 - Preheat the oven to 350°F. Grease an 8x8-inch baking dish thoroughly.
02 - In a large bowl, combine sliced apples with lemon juice, granulated sugar, cinnamon, nutmeg, and flour. Toss until apples are evenly coated. Transfer the mixture into the prepared baking dish, spreading evenly.
03 - In a separate bowl, mix rolled oats, flour, brown sugar, cinnamon, and salt. Incorporate the cold cubed butter with fingers or a pastry cutter until the mixture forms coarse crumbs.
04 - Evenly scatter the crisp topping over the apple layer. Bake for 40 minutes, or until the topping is golden and the apples are bubbling.
05 - Allow the dish to cool slightly before serving. Serve warm, optionally accompanied by vanilla ice cream or whipped cream.