Once the dough has chilled for 2 hours OR overnight, it is ready to laminate. First bring your butter slab out of the fridge and place it on the counter so it has a few minutes to soften just *slightly.* Our aim is to have the butter slightly pliable but not soft — similar in texture to the chilled dough.
Turn dough out onto a lightly floured surface and roll it out into a large rectangle, roughly 8"x16". (It needs to be slightly larger than twice the length of the butter slab.) Use a pastry brush to dust off any excess flour from the surface of the dough. Place the butter slab on one side, leaving a border, then fold the dough over to envelop the butter. Pinch around the edges to seal in the butter tightly.
Note: While laminating the dough, use as much all-purpose flour as needed to keep your dough from sticking to the work surface and to your rolling pin. We will use a pastry brush between steps to brush off any excess flour.
Roll the dough out to roughly 24x9". Use a pastry brush to dust off excess flour. Perform one single turn: Fold the dough in 3rds like a letter.
Place the dough back in the sealed container (or wrap it tightly with parchment/plastic). Place in the fridge and chill for at least 1 hour before proceeding. This is necessary to keep the butter from softening too much, and it will allow the gluten to relax so the dough will not resist being rolled out again.
Once the dough has chilled, roll it out again to 24x9". Again, use your pastry brush to dust off excess flour. Now perform a double turn: Fold both ends of the dough to meet in the center, then fold in half again like a book. Cover dough and refrigerate for 1 hour OR overnight to allow the gluten to fully relax.