Preheat oven to 375°. Place the baking rack at the lowest level of the oven. Press pie crust into a 9-inch pie plate (crimp or pleat crust edges). Line top of crust with foil, place on a baking sheet and bake 20 minutes.
Peel and slice the apples and set to the side.
Combine the brown sugar, apple pie spice, and salt. Then, to make the topping. In a separate bowl take half the sugar mixture (about 3/4 cup) with 1 1/2 cups all purpose flour, and the butter. Using the tines of a fork (or a pastry cutter) place cubed cold butter into flour mixture. Mix until pea-shape pieces of flour appear. Set to the side.
Combine the remaining sugar with the remaining 1/4 cup all purpose flour. Add the sliced apples to the bowl. Toss until well coated.
Fill the apple mixture into the pie crust. Top evenly with the crumb mixture. Bake for 30 minutes. Then, carefully remove the tinfoil off the top of the crust. Bake for an additional 25-30 minutes. Let the pie rest for at least 1 hour before cutting into it.