For the Pastry
Whisk the flour, salt and sugar together in a large bowl. Using a standard box or potato grater, grate the frozen butter into the flour and toss lightly with your fingers until it is thoroughly combined. Sprinkle in ice water and mix with your fingers until the dough comes together in a ball. Divide it into two pieces, making sure one half is slightly larger than the other. Wrap in plastic wrap, flatten and chill for at least 30 minutes or even overnight. Resting will help tenderize the pastry and make it easier to roll.
Remove the pastry from the refrigerator and allow it to warm slightly, just until it is pliable. Lightly flour your hands, the rolling pin, your work surface and the dough. Roll out the larger pastry disc into a circle large enough to slightly overlap the edges of an 8-inch glass pie dish. Transfer the dough to the pie dish by folding it into quarters then unfolding it in the dish.
Preheat your oven to 375 degrees.
For the Filling
Toss the apples with the brown sugar, cinnamon and flour. Add the apples to the bottom crust then roll out the remaining smaller disc and carefully place over the top of the pie. Roll and crimp the edges of the dough together, tightly sealing them. Poke a few vent holes into the top of the pie and place on the bottom rack of oven. Bake for 1 hour, until the crust is golden and juices are bubbling.