Make the all-butter pie crust. In a large bowl, stir together the flour, granulated salt, and salt. Add the butter. With a pastry cutter or a fork, quickly cut the butter into the flour mixture until mostly pea-size pieces of butter remain (a few larger pieces are okay).
In a large measuring cup or a small bowl, combine the water, ice, and vinegar. Sprinkle 2 tablespoons (30 ml) of the ice-water mixture over the flour mixture and mix with a spatula until the water is fully incorporated. Add more of the ice-water mixture, 1 to 2 tablespoons (15 to 30 ml) at a time. Using the spatula or your hands, mix until the dough comes together in a ball with some dry, shaggy bits remaining. Squeeze and pinch the dough with your fingertips to bring all the dough together, sprinkling dry bits with more small splashes of the ice-water mixture, if necessary, to combine.
Shape the dough into a flat disk, wrap it in plastic, and refrigerate the dough for at least 1 hour (or overnight), to give the dough time to rest.
Make the strawberry filling. In a medium saucepan over medium heat, combine the strawberries, orange juice, granulated sugar, and salt. Cook the mixture for about 10 minutes, stirring frequently, until some of the strawberries break down and some remain whole but soft. Remove the filling from the heat and allow it to cool.
Preheat the oven to 350°F (177°C). Line a large baking sheet with parchment paper.
On a floured work surface, roll out the disk of dough until it reaches ¼ inch (6 mm) in thickness. Using a 2- or 3-inch (5- or 7.5-cm) cookie cutter, stamp out an even number of circles. Place a large spoonful of the strawberry filling in the centers of half of the dough circles. Take a second dough circle and gently lay it on top of a filled circle. Using the tines of a fork, press down on the edges to seal the hand pie. Once all the hand pies have been sealed, use the fork to prick holes in the tops to allow steam to escape during baking. Transfer the hand pies to the prepared baking sheet.
In a small bowl, whisk together the egg and water. Brush the egg wash on the hand pies.
Bake the hand pies for 24 to 28 minutes, until they are golden brown. Remove the hand pies from the oven and allow them to cool on the baking sheet for 10 minutes. Transfer the hand pies to a wire rack to cool completely.
Make the royal icing glaze. In a medium bowl, whisk together the powdered sugar, milk, vanilla, and food coloring (if using) until the glaze reaches a spreadable consistency. Add more milk if needed.
Using the back of a small spoon, spread a thin layer of the royal icing glaze on each cooled hand pie. To garnish the hand pies, arrange the edible flowers on top of the glaze before it sets.