Prep the apples. Preheat the oven to 350°F (180°C). Then peel, core, and slice the apples.
Make the fruit base. In a large bowl, toss together the apples, maple syrup, arrowroot powder, lemon juice, vanilla, and cinnamon, until well combined.
Place in baking dish. Transfer the apple mixture to a 9 x 13-inch baking dish.
Make the apple crisp topping. In a medium bowl, whisk together the almond flour, coconut sugar, cinnamon, and salt. Using a pastry cutter or fork, cut in the butter until the mixture becomes crumbly. Then stir in the rolled oats.
Add the topping and bake. Sprinkle the apple crisp evenly over the sliced apples in the baking dish. Bake for 45 to 50 minutes, or until the topping is golden brown and the apples are soft.
Serve. Scoop a portion out and serve warm. You can also add a scoop of ice cream or whipped cream on top.