Preheat oven to 350° F. In a medium bowl, add almond flour, cornstarch, melted butter, maple syrup and vanilla extract. Stir with spatula until well mixed, transfer to prepared baking dish and flatten with hands and spatula into an even layer. Bake for 15 minutes.
Remove crust from the oven and very carefully pour filling on a side on top (abrupt pouring will lift the crust). Place back in the oven and bake for 15-20 minutes or until firm but still a bit jiggly in the middle.