Preheat oven to 350°F. Grease an 8x8-inch baking dish.
In a large bowl, combine sliced apples, maple syrup, cornstarch, lemon juice, cinnamon, nutmeg, and vanilla extract. Let sit for 10 minutes.
In a separate bowl, mix together oats, flour, brown sugar, and salt. Add melted butter and mix with your fingers until the mixture resembles coarse crumbs.
Spread the apple mixture in the prepared baking dish. Evenly sprinkle the crisp topping over the apples.
Bake in the preheated oven for 45 minutes, or until the topping is golden brown and the apples are bubbly.