Preheat oven to 450°F. Place squash on a parchment or foil-lined baking tray cut side down. Roast until very soft, about 45 minutes. Let cool and scoop the flesh out of the squash. Purée in a food processor until smooth. Reduce oven to 350°F. Whisk together 2 cups of squash purée, maple syrup, cream, eggs, and vanilla. Whisk in flour and spices until thoroughly combined. Pour into prepared crust. Bake about 45-50 minutes until set but center still jiggles. Check the pie after 35 minutes and if the crust is well browned, cover the edges with a ring of foil. Remove from oven and let cool. If desired, serve with whipped cream or vanilla ice cream.