Preheat oven to 350°F (175°C). Lightly grease your baking dish.
In a large bowl, toss the sliced apples with lemon juice, maple syrup, cinnamon, nutmeg, cornstarch, and vanilla until evenly coated.
Spread the apple mixture evenly into the prepared baking dish.
In a medium bowl, mix oats, flour, brown sugar, cinnamon, and salt.
Pour in the melted coconut oil and stir until the mixture becomes crumbly.
Sprinkle the crisp topping evenly over the apples.
Bake uncovered for 40 minutes, or until the topping is golden and the apples are bubbling.
Let cool for 10 minutes before serving.