In a large bowl, whisk together flour and salt. Scatter cubed butter over top, then use a pastry cutter to work it into the flour until the mixture resembles coarse crumbs. (Or pulse in a food processor.)
Sprinkle 6 tbsp ice water over top, and use a stiff rubber spatula to gently stir and press the dough together. Add more water only if needed to get the dough to stick together. Dump the shaggy mixture onto a lightly floured counter, and divide into two even piles. Gently press each pile into a disk, and wrap with plastic wrap. Refrigerate 1 hour, or up to 48 hours.
Preheat oven to 500ºF. Roll out one disc (keep the second one in the freezer for another pie!) between sheets of parchment paper placed on top of a dampened paper towel (this anchors the parchment to the counter). You're aiming for a large rectangle, dimensions don't really matter. Transfer the dough to a large baking sheet and peel off the top layer of parchment paper (reserve it). Pop the whole pan in the freezer for 10 minutes to make sure the dough isn't too soft.
Combine filling ingredients in a large bowl, then dump them onto one end of the pie dough. Fold the dough over the filling and press it to seal (link to pictures in the post). Cut a couple of steam vents with scissors or a sharp knife. Place pie on bottom oven rack, reduce oven temperature to 400ºF and bake until crust is deeply golden and filling bubbles out of the steam vents, about 45 minutes.