8-12 hours later take the dough and the butter book out of the fridge. Place the dough bottom side up on a floured surface and pat it out with your fingers. Roll it out to shape of a rectangle. With the width of the rectangle facing you, place the butter book perpendicular to the dough (see photos for example). Fold the sides of the dough over the butter so that the dough ends meet perfectly in the middle without overlapping. If the dough isn't the right size, remove the butter, and roll out a bit more until it's the perfect fit.
If you would like to add wonderful flavor, aroma, and the added nutrition of a sourdough culture, simply add 60 grams (about 1/4 cup) of a ripe sourdough culture to the dough when mixing.
You STILL need to use the same amount of dry baker's yeast as well because the dough won't rise enough without it.