Place oven rack in lower third of oven, and preheat oven to 450°F. Brush 4-qt. Dutch oven with oil, set on oven rack, and heat until sizzling hot. Transfer dough to Dutch oven. (Don’t worry if dough is lopsided and ragged-looking; it will even out during baking.) Brush top of dough with water, then sprinkle with coarse salt, if using. Slash large X in top of dough with knife or kitchen shears; cover pot, and shake to center dough.