In a large bowl, whisk together flour, sugar, and salt.
Use your fingers to break up butter and cut it in, until mixture resembles mostly coarse meal with a bunch of hazelnut-size pieces remaining.
Drizzle with ice water and stir with a fork until most of flour is moistened (mixture will still be shaggy and not at all formed into a dough). If there is dry flour remaining, add more ice water, 1 tablespoon at a time, until a piece will hold together when pressed between your fingers.
Turn dough out onto a clean surface and gather into a mound. Using the heel of your hand, smear dough away from you, working your way down to create long layers of butter. Fold dough over onto itself, as if closing a book. Repeat twice more. (There should be plenty of large, flat pieces of butter visible in dough.)
Divide dough into two pieces, one about 12 ounces, the other about 1 pound. Pat smaller piece into a round and larger into a rectangle.
Wrap each loosely in plastic, then use a rolling pin to flatten and finish compacting (use plastic rather than your hands to maneuver dough—the less body heat transferred, the better). Refrigerate until firm, at least 1 hour and up to 1 day.