For pastry, sift flour and salt together in a large bowl. Cut in shortening with a pastry cutter or 2 knives until mixture resembles coarse meal. Make small depressions in the mixture and drizzle in up to 5 tbsp. ice water, 1 tbsp. at a time, mixing until dough holds together. Form into a ball, wrap in plastic wrap, and refrigerate for 1 hour.

For filling, gently mix blueberries, sugar, lemon juice, and cornstarch together in a large mixing bowl.

Preheat oven to 400°. Divide dough into 2 equal balls. Roll out 1 dough ball into a 12" round on a floured surface, then ease into a 9" pie pan. Fill pastry with blueberries and dot with butter. Roll out remaining dough into a 12" round, place on top of berries, then fold edge under and crimp or flute.

Pierce top crust with a small sharp knife in several places to allow steam to escape during baking. Bake for 10 minutes, then reduce heat to 350° and continue baking until crust is golden brown, about 30 minutes. Allow to cool before serving.