A proofing basket is a round, oval or long basket, usually out of wicker that helps prevent particularly wet doughs from flowing when they proof. You can line them with cloth, or do as I do and cover them in abundant quantities of four to prevent sticking. This is also why you dust your kitchen towel with a lot of flour when you use a bowl and towel. The moisture in the dough will (and I mean will) make it stick to a dry cloth, and it will tear up when you are ready to take it out of the basket.
For a whole-wheat or rye version, replace 100-200 grams of the all-purpose flour with the same amount of whole-wheat or rye. You will need a little bit more water. If the dough is stiff, blend in water by wetting your hands before continuing to knead.
A large or wide Dutch oven will allow the bread to flow, making it a bit flat and wide. A more narrow pan will force it to rise up. The taste is the same, the way it looks in the only difference.
Baking with the closed lid takes away the need to inject steam in the oven as the moisture coming out of the dough is trapped in the closed pan. The result will be a crisp but thin crust.
Because you bake the bread with the seams of the folds on top, you will also not have to cut the bread. It will tear at the folds, which are the weak spots in the dough.