Preheat oven to 350 degrees (you will need a 9x9 baking dish for this recipe, but no need to grease it).
Make the apple filling: In a large bowl combine your diced apples, lemon juice, and vanilla.
In a separate small bowl combine your sugar, cornstarch, salt, and cinnamon and stir to combine. Add this mixture to your apples and stir until all of the apples are evenly coated.
Add the apples to a 9x9 baking dish and bake them in a preheated oven for 10 minutes, and then remove from oven.
While your apples are prebaking, making the oat crumb topping: Combine oats, almond flour, cinnamon, and salt (and optional pecans) in a medium bowl and stir to combine.
In a separate small bowl stir together your melted coconut oil, maple syrup, and vanilla. Add this mixture to your dry ingredients and stir until everything is completely coated and evenly combined.
Evenly spread your crumb topping to the top of your apples and bake for another 40-50 minutes or until the topping is golden brown. Let cool for at least 20-30 minutes before serving for best results. Serve with coconut milk whipped cream or vanilla ice cream.