Sift the flour and salt into a large bowl. Cut in the butter, using a pastry blender, 2 knives or your fingers. Leave the butter in large chunks (about ¼inch). Stir in just enough cold water to hold the dough together. At this point, the dough will look lumpy and not blended.
Transfer the dough to a floured surface and roll it out to a 16-x-12-inch rectangle. Use a pastry scraper to fold the dough in thirds, as you would fold a business letter. Rotate the dough 90 degrees, so the open side is to your right; this is called a single turn. Give the dough 3 more single turns, rolling it out to a 16-x-12-inch rectangle, folding it in thirds, and rotating 90 degrees for each turn. The dough will become smoother and more homogenous with each turn.
Divide the dough into 3 equal portions, cutting straight through the dough with a sharp knife. Wrap each portion individually in plastic wrap. Chill for at least 2 hours or overnight before rolling out.