Pie Crust:

• Prepare Homemade Flaky Pie Crust according to the recipe. Let it rest for at least 2 hours in the refrigerator before rolling it out. I prefer to make the dough a day in advance to give it enough time to rest and chill. Also, the colder the dough, the easier it is to work with.
• Lightly flour your work surface. Take one chilled dough disc and roll it out with a rolling pin. Use light pressure and turn the dough after every few rolls until you have about a 12-inch circle. Fold dough in half (it's easier to transfer it into the pie dish that way) and carefully place it in a 9-inch pie dish and unfold. Make sure you smooth it along the edge and tuck it in nicely. Put back in the refrigerator.
• Take the other disc of chilled pie dough and roll it out like the first one. Use a pizza cutter or sharp knife, and cut six 1-inch strips and 12 small stars with a star cookie cutter. Put them back in the refrigerator.

Pie Filling:

• Preheat the oven to 400°F or 200°C.
• Wash all the berries. Then cut the strawberries into ½-inch chunks and place them in a big mixing bowl with the raspberries.
• In a smaller bowl, add the blueberries and the blackberries.
• Add the sugar, arrowroot powder (or cornstarch), and flour into another small bowl.
• Scrape out the vanilla seeds from one vanilla bean “pod” by laying it flat on a cutting board and slicing it down the middle, lengthwise, midway through the pod. Then open it up slightly and run a dull knife or a small spoon down the length of the pod to collect all the seeds and add them to the sugar mixture. Mix well.
• Add 1/4 of the sugar vanilla mixture to the blueberries/blackberries with 1/2 tsp of vanilla extract and combine.
• Pour the remaining 3/4 of the sugar mixture to the strawberries/raspberries with 1 tsp of vanilla extract and mix it up.

• Take aluminum foil and fold it a few times to create a strip; create a 90° angle with it and place it in the upper left-hand corner of the pie. Then scoop the blueberry/blackberry filling into it. The foil will keep the filling nicely in place.
• Add the strawberry/raspberry filling to the remaining 3/4 of the pie. If there is any extra liquid from the berries, try not to add that to the pie, or you will end up with a soggy mess where the filling doesn't set correctly.
• Remove the foil wedge.
• Take the dough stars and stripes out of the refrigerator. To create an American flag design, place the strips parallel to each other, onto the red (strawberry/raspberry) and the stars on the blue filling (blueberry/blackberry). Cut any excess dough from the strips and pinch them nicely to the edge of the crust.
• With a food brush, brush the stars and stripes with egg wash (crack an egg into a small bowl and mix it up) and sprinkle with coarse sugar, if desired.

Baking:

• Put the pie dish on a large baking sheet and place it in the oven—Bake for 20 minutes at 400°F or 200°C. After 20 minutes, carefully take the pie out of the oven. Place a pie crust shield along the edge of the pie. If you don't have a pie crust shield, use aluminum foil, just cut the center out to cover the edge of the crust. That prevents the crust from browning too quickly.
• Turn the oven down to 350°F or 180°C and place the pie dish back inside. Bake for another 40-45 minutes, or until golden brown and the filling inside is bubbling. It all depends on how strong your oven bakes. Keep a close eye on your pie.
• Let the pie cool for at least 3 hours before you cut into it. It will allow the filling to thicken. Serve with some ice cream or as is.