Lightly flour your work surface and place the chilled dough on top. Roll it out into a square about 12"x12".
Unwrap the butter slab and place it in the middle of the dough square, off-set so it looks like a diamond inside.
Fold the dough flaps over the edges of the butter until they meet in the middle, then pinch and seal the edges. You can use a little water on your fingers if necessary to get the dough to stick together.
Dust with flour, flip the dough package over, and tap it gently with the rolling pin, forming it into a rectangular shape. Pick up the dough and check that it isn't sticking underneath; if it is, lightly flour the surface, then roll from the center out until you have a 10"x20" rectangle.
Take a dry brush and sweep off any excess flour. Fold the bottom third of the dough into the center, then the top third over it, like it's a business letter. Be sure to line up the edges. This is the first "turn."
Take the left side of the dough letter and fold it over to the right side, making a sort of book. This is the second "turn."
If the dough is still cool enough, you can repeat the above. You have to be careful it doesn't get too warm or the butter will all squeeze out.
Wrap the dough package and return to the refrigerator for at least 30 minutes.
Repeat the above for turns 3 and 4.
Wrap the dough well and refrigerate for at least 1 hour, preferably overnight. (I only lasted 1 hour.)