Levain Storage: Put the hunk of reserved dough (about 6 ounces) in a covered jar with 1 1/2 cups of warm water. This is the levain, which will go into the next loaf. Let stand at room temperature for 12 hours, then refrigerate. The levain will keep for up to 10 days; freeze for longer storage.
Toppings: Feel free to experiment with different seeds like sesame, poppy, or caraway, or simply dust with flour for a traditional look.
Storage: Store cooled bread in a paper bag at room temperature for 2-3 days, or freeze slices for longer storage.