Preheat oven to 350°F (175°C). Lightly grease an 8x8-inch baking dish.
In a large bowl, toss apple slices with cinnamon, nutmeg, and sugar. Spread evenly in the baking dish.
In another bowl, mix oats, almond flour, brown sugar, cinnamon, and salt. Add butter and cut it in with a fork until the mixture is crumbly.
Sprinkle the topping evenly over the apples.
Bake for 35–40 minutes, or until apples are tender and the topping is golden brown.
Let cool slightly before serving. Enjoy warm with ice cream, whipped cream, or Greek yogurt.