Prepare the Crust: Using your fingers, mix together flour, butter, and salt in a large bowl until butter is well incorporated. Gradually sprinkle 2 to 4 tablespoons very cold water into mixture, kneading as you add water, until dough just comes together. (You may not need to add all the water.) Turn dough out onto a lightly floured work surface; knead until it forms a smooth ball, 2 to 3 times. Divide dough in half, and shape into 2 disks. Wrap each disk in plastic wrap; chill at least 2 hours or up to overnight.

Unwrap 1 chilled dough disk, and place on a lightly floured work surface. Let stand at room temperature until slightly softened, about 5 minutes. Sprinkle with flour; roll into a 12-inch circle. Carefully fit dough round into a 9-inch deep-dish glass pie plate, leaving a 1 1/2-inch overhang around edges. Refrigerate until ready to use.

Prepare the Filling: Preheat oven to 425°F with oven rack in lowest position. Stir together apples, sugar, flour, cinnamon, and salt in a large bowl until apples are evenly coated. Spoon mixture into prepared piecrust; sprinkle mixture with butter.

Unwrap remaining chilled pie dough disk, and place on a lightly floured work surface. Let stand at room temperature until slightly softened, about 5 minutes. Sprinkle with flour; roll into a 12-inch circle. Cut into 12 (3/4-inch-wide) strips. (Discard remaining dough scraps, or use for another purpose.) Arrange strips in a lattice design over Filling; trim strips as needed to meet the bottom Crust overhang. Fold dough edges under, and crimp using your fingers or a fork.

Place assembled pie on a rimmed baking sheet. Bake in preheated oven 15 minutes. Reduce oven temperature to 350°F (leaving pie in oven); continue baking 45 minutes. Cover loosely with aluminum foil to prevent excessive browning; continue baking until juices are thick and bubbly, Crust is golden brown, and apples are tender when pierced with a long wooden pick, about 30 minutes. Transfer pie to a wire rack, and cool at least 1 hour.