Preheat the Oven. Preheat your oven to 350°F and lightly grease an 8x8-inch baking dish or a similar-sized oven-safe dish.
Prepare the Apple Filling. Peel, core, and slice the apples into thin wedges. Place them in a large mixing bowl and toss with lemon juice, maple syrup, cinnamon, nutmeg, and cornstarch until evenly coated.
Make the Topping. In a separate bowl, combine the oats, almond flour, melted coconut oil or butter, maple syrup, cinnamon, and a pinch of salt. Mix until the ingredients are well combined and crumbly.
Assemble the Crisp. Spread the apple mixture evenly in the prepared baking dish. Sprinkle the oat topping over the apples, covering them completely.
Bake. Bake the apple crisp in the preheated oven for 35-40 minutes, or until the apples are tender and the topping is golden and crispy.
Serve. Let the apple crisp cool for a few minutes before serving. Enjoy it warm, either on its own or with a scoop of vanilla ice cream or a dollop of Greek yogurt for an extra treat.