Preheat the oven to 350 degrees F. Spray a 15-by-10-by-1-inch pan with nonstick cooking spray and set aside.
In a large bowl, mix the salt, 4 cups of the flour and 1 teaspoon of the sugar. Using a pastry blender, cut in the butter until the mixture looks like coarse crumbs. Add 1 tablespoon of the water at a time to moisten it and mix, repeating until a dough starts to form. Knead the dough into a ball. Divide the dough in half and flatten each half into a rectangle. Wrap with plastic wrap and refrigerate for at least 2 hours.
Lightly flour a work surface and roll 1 piece of dough into a 19-by-13-inch rectangle. Place the dough on the prepared pan and ease it onto the pan and up the sides, making sure not to stretch the dough too much so it doesn't become too thin. Trim the leftover dough, leaving just enough to cover the sides of the pan. Fold the dough as desired on the edges.
In a large bowl, combine the apple slices, cinnamon and remaining 1/3 cup flour and 1/2 cup sugar. Toss until the apples are coated. Arrange the apple mixture evenly on the dough.
On a lightly floured surface, roll the remaining piece of dough into a rectangle. With leaf-shaped cookie cutters, cut out dough leaves. Arrange the leaves on top of the apple mixture to cover the pie; it is okay to leave some space in between the leaves so you can see the apple filling. Brush the egg wash on top of the leaves.
Bake until the apples are cooked through and the top crust is evenly golden brown, 40 to 45 minutes. Serve with a scoop of vanilla ice cream and enjoy!