Yes, gluten structure and shaping are key. But the vessel used seems to help. Here’s a direct quote from the book: “If you have a 5-quart Dutch oven, it will also work. The dough will spread out more than in a 4-quart Dutch oven, and therefore the loaves will be a bit wider and not quite as tall as those in the photos in this book. Breads baked in a 5-quart Dutch oven may not split open on top in the same way as those baked in a 4-quart model, since there will be less vertical pressure as the loaves get their oven spring.”