Add the butter to the bowl and use a dough hook to mix the dough at low speed on the stand mixer until the flour is fully moistened. The dough will look shaggy at this point. Cover the bowl with plastic wrap and allow it to rest for 20 minutes.
Add the salt and use the stand mixer to knead the dough on medium speed (i.e., #4 on a KitchenAid stand mixer) for 8-10 minutes. Continue kneading until the dough is smooth and comes away from the sides of the bowl. The dough will still be slightly sticky.
Remove the dough from the stand mixer bowl using a greased spatula or bench scraper and place into a large, oiled bowl. Lightly oil the surface of the dough and cover the bowl tightly with plastic wrap.
Let the dough rise at room temperature (approximately 75-80°F/24-27°C) until it has doubled in volume. This should take approximately 1-2 hours.
Turn the dough out onto a floured surface and use your fingers to press it gently into a rectangle. Try to keep as many of the air bubbles as possible while shaping it (i.e., don’t remove all of the air bubbles). Give the dough 2 letter turns and then place it back into the bowl to proof again. To do a letter turn, fold one third of the dough over the center third, then fold the remaining third over the rest of the dough. This is the same process you would do to folder a letter that is put into an envelope.
Let the dough rise at room temperature (approximately 75-80°F/24-27°C) until it has doubled in volume. This should take approximately 1-2 hours.