Whisk together the flour and salt in a large bowl.
Cut the cold butter into small cubes (about 40 cubes per stick of butter). This will make it easier to cut the butter into the flour!
Drop the butter pieces into the flour mixture, keeping them as separate as possible. Using a pastry cutter, cut the butter into the flour, aiming for bean-size pieces of butter. Larger pieces of butter will result in very flaky pie dough, so do not overwork the dough or aim for a fine, even texture.
Pour the water in, a few tablespoons at a time, and fluff the flour mixture using a fork, dragging the bottom of the mixture up through the water. Use all of the water*; there will still be a lot of dry flour and shaggy bits in the bowl, but do not be tempted to add more, or the dough will be too sticky to work later.
Turn the contents of the bowl out onto a clean counter. Knead together by hand. Press the mixture together, then begin folding it, scooping the remaining dry bits of flour onto the center of the dough before folding. Continue to fold and knead until no dry bits of flour are left and the dough comes together smoothly. The more times you fold, the more flaky layers you will end up with.
Divide the dough in half. Wrap tightly in plastic wrap and press down into 1″ thick discs. Chill in the fridge for 30 minutes, or up to 2 days. (Beyond 2 days, the dough will begin to turn gray; to avoid this, double-wrap the discs and store in the freezer until ready to bake.)