Preheat oven to 425°. For pie crust, stir together flour and salt in a large bowl. Cut in shortening using a pastry blender until pieces are pea-sized. Sprinkle 1 tablespoon ice water over flour mixture, gently toss with a fork. Repeat with additional ice water, 1 tablespoon at a time, until all of flour mixture is moistened. Gather dough into a ball. Divide dough half; shape each portion into a ball.

Slightly flatten 1 pastry ball on a lightly floured surface. Roll from the center to the edge to create a 12-inch circle. Fold pastry into quarters; unfold in a 9-inch round pie plate. Ease pastry into pie plate; do not stretch. Trim pastry to within ½-inch of pie plate edge.

For filling, combine apple slices, sugar, flour, lemon juice, cinnamon, and salt in a medium bowl; toss to coat evenly. Transfer apple pie filling to the pastry-lined pie plate.

Roll out remaining dough ball on a lightly floured surface to a ⅛-inch-thick rectangle. Cut into strips. Weave strips over apples. Tuck ends of strips under bottom crust edge and crimp edges to seal. Lightly brush pastry top with beaten egg; sprinkle with coarse sugar.

Bake for 20 minutes. Reduce oven temperature to 375° and bake for 30 more minutes or until filling starts to bubble in center. Cool on a wire rack.