The dough is roughly rounded first, then rested on the counter for 15 to 30 minutes, and finally given its final shape. This pause allows the gluten stretched during preshaping to relax. Dough that is not rested resists and pulls back during final shaping, and its surface tears, which leads to uneven oven spring.
During preshaping, the dough is gathered, folded, and its surface is tightened; this stretches the gluten strands in a particular direction. When stretched gluten is immediately stretched again, it resists and pulls back; if forced, its surface tears. Resting releases this tension: the strands slowly settle back into place, and the dough can be shaped again. The same principle applies when rolling out yufka (paper-thin flatbread) and pizza dough, which also need to rest.
The rest is usually 15–30 minutes. Tight, high-protein doughs need the upper end of that range, while soft, wet doughs need the lower end. You can also tell by checking the dough: if it does not resist a gentle fingertip press and the indentation slowly closes, it has relaxed. Resting too long causes problems too; the dough spreads, loses the tension gained during preshaping, and must be shaped again from the beginning. This rest takes longer for dough coming out of the refrigerator because gluten is firmer when cold and takes time to relax.
Preshaping is like a small rehearsal for the final shape. The dough is divided, and each piece is roughly rounded and gathered; the goal is not a perfect ball but a smooth surface. Arrange the pieces with space between them on the counter and cover them with a towel or plastic wrap; an uncovered surface dries out and forms a skin during final shaping. This step also evens out the pieces; pieces divided by weight become more alike as they rest. Their weights are also made equal at this stage using a scale; uneven pieces bake for different lengths of time.
Skipping the step causes problems in several ways. The dough keeps pulling back during final shaping and will not reach the desired length or roundness. The forced surface tears, and gas escapes through those tears during proofing. Oven spring becomes uneven, and the loaf leans to one side. Tired dough also produces a tight crumb. These flaws can all be prevented by half an hour of resting, and skipping it to save time comes at a cost.
This step is most necessary for shaped yeasted doughs such as bread, pide (Turkish flatbread), pizza, and simit (sesame-crusted bread rings). It is not needed for doughs poured into a pan because the pan gives them their shape. Yufka (paper-thin pastry sheets) and mantı (Turkish dumpling) dough, however, rest before rolling and benefit in the same way. Cookie and tart dough rests for another reason: to firm up the fat. In short, wherever gluten is stretched, there is a rest step, and its length depends on how tight the dough is. The time also shortens depending on which batch of dough you are working on that day; as the counter warms up, the dough relaxes more quickly.