No you don't need to cover your loaf pan sourdough bread, you can bake it uncovered in your oven at 200C/392F for 45 minutes. A spritz of water before you place it into the oven is a good idea and provides a little steam but it's not essential. You can place a loaf pan of the same size as you're using to hold your dough on the top to create a mini Dutch Oven, but it's definitely not essential.