For the pie crust: fit the dough into a lightly greased pie plate and crimp around the edges. Pop the crust into the freezer so that it's firm when it's time to assemble the pie. Preheat the oven to 400℉.
To make the crumble: combine the all purpose flour, sugar, cinnamon, and salt in a bowl. Using your fingers or a pastry cutter, cut the butter into the flour mixture, breaking up the pieces and incorporating them into the flour. While you're working in the butter, squeeze the mixture in your hands to make varying-sized crumbs--there should be a mix of big crumbs and fine crumbs. Place the finished crumble in the fridge while you make the pie filling.
To make the blueberry pie filling: combine the blueberries, shredded apple, sugar, lemon juice, and zest in a large bowl. Gently mix to combine the ingredients.
In a small bowl, combine the flour and cornstarch. Sprinkle the cornstarch mixture over the blueberries and gently fold the ingredients together until all the berries are coated.
Pour the pie filling into the frozen pie crust. Top with the crumble, making sure to be generous around the edges of the pie (this will help catch bubbling over).
Place the pie onto a sheet pan and bake at 400℉ for 15 minutes. After 15 minutes, do not open the oven door, but reduce the temperature to 350℉ and continue baking for another 50-70 minutes until the pie is browned, puffed in the middle, and berry juice is bubbling around the edges. The pie is fully baked when the center of the pie's internal temperature reads 175℉ on an instant read thermometer.
Remove the pie from the oven and let set a minimum 5 hours or overnight. You can cool the pie at room temperature or in the refrigerator. Once the pie has set, slice and enjoy!