Turn the proofed dough out onto a generously floured work surface, and gently roll & pat it into a log. Cut the log down to 6 or 8 equal portions (6 for 1/2lb burgers, 8 for 1/4lb burgers), and cover the pieces with plastic wrap or a tightly woven towel.
With one portion at a time, lift & fold the edges of the dough over the center, and press down into the middle. Fold in north, south, east, west, then halfway in between the first folds, for a total of 8 folds. After that, the dough ball should feel noticeably tighter than when you started.
Pinch the folds on the bottom of the ball firmly together, and then gently roll it between your hands to get it as round as possible. Set it aside on a parchment-lined baking sheet, and repeat with the rest of the dough pieces.
Cover the baking sheet with a clean dish towel, and let the buns rise a second time until they are double or triple their original size. This can take anywhere from 3–6 hours, depending on how warm your kitchen is and how active your starter is.