Cut your chilled butter sheet in half. Lay one piece of butter over two-thirds of your dough rectangle. Fold the dough section without butter over the butter layer, then fold the remaining buttered end over the top of that, creating three layers of dough. Chill the folded dough again; an overnight chill is recommended to make it easier to work with the next morning.
The next morning, or after a long chill, gently roll the folded dough back into an 8x12 inch rectangle. Take your remaining piece of chilled butter and lay it over two-thirds of the dough, just as you did before. Fold the dough in thirds again. Carefully roll the dough once more to an 8x16 inch rectangle and fold it into thirds one last time. Return it to the refrigerator for another chill.