Prepare a large rimmed baking sheet (at least 15 x 10-inches) by lining with parchment paper. Set aside.
Liberally sprinkle a work surface with flour. Unwrap the larger portion of dough (the 2/3rds one) and place it on the work surface, sprinkling its top with flour. This portion will be your base crust. If the dough is hard, let it rest for a few minutes. If the dough seems too sticky at first, add flour liberally. Use a rolling pin to roll with light pressure, from the center out, moving the pie dough around every quarter to roll it evenly. Roll the the dough to a rough oval that is about 15-inches long, 10-inches deep, and about 1/4-inch thick. Transfer this oval onto the prepared baking sheet and refrigerate while you roll out the remaining disk.
Replenish your work surface with more flour. Repeat step 2, this time rolling the dough out to a smaller oval that is about 13-inches long and 9-inches deep. This portion will be your top crust. Transfer the rolled out dough on to a piece of wax or parchment paper. Use your numerical cookie cutters to stamp out the Pi number sequence, dipping the sharp edge of each cutter in flour before doing so. Once your numbers have been stamped, transfer the crust into the freezer to chill while you fill the bottom crust with pie filling.
Remove the base crust from the refrigerator and use a spoon or a rubber spatula to transfer the fruit filling to the center of the crust. Spread out the filling evenly over the base, but leave a 2 to 3-inch border all the way around the oval. Evenly dot the fruit filling with 2 tablespoons of unsalted butter specks.
Remove the top crust from the freezer and gently, carefully lay the crust over the fruit filling. There should still be a 1 1/2 to 2-inch border visible from the base crust. Working quickly, fold this border over the top crust, overlapping when necessary and pressing gently to adhere to the folds. Use a fork to press down on the border to "seal" and "crimp" the bottom crust onto the top crust. Transfer the pie to the refrigerator to chill while you preheat the oven.
Center a rack in the oven and preheat the oven to 375 (F). While the oven is heating, whisk 1 large egg in a small bowl.
When the oven is ready, remove the pie from the fridge. Working quickly, use a pastry brush to brush the top and border of the pie. Sprinkle evenly with 1 tablespoon granulated sugar and transfer immediately to the preheated oven. Bake until the crust is golden brown and filling is bubbling, 30 to 35 minutes. Transfer to a wire rack, and let pie cool until it is just warm to the touch, about 45 minutes. Slab pie is best eaten the same day it is baked, but it can be kept at room temperature, loosely covered with plastic wrap, for up to 2 days.