Preheat oven to 350°F (175°C).
Prepare the apples: Peel, core, and slice the apples evenly. Place them in a large bowl.
Toss apples with lemon juice and granulated sugar. Set aside.
Make the crumble topping: In a separate bowl, mix flour, oats, brown sugar, cinnamon, and nutmeg.
Add butter: Using your fingers or a pastry cutter, work the butter into the flour mixture until it forms pea-sized clumps.
Assemble the crisp: Grease an 8-inch round baking dish and layer the apples on the bottom. Spread the crumble topping evenly over the apples.
Bake for 40-45 minutes, or until the topping is golden brown and the apples are tender.
Cool for 10 minutes before serving. Enjoy warm with a scoop of ice cream or whipped cream.