This recipe recreates the light, open-crumbed focaccia we ate in Bari, Italy. To achieve that texture, the dough must be wet—so wet, in fact, it verges on a thick, yet pourable batter. Resist the temptation to add more flour than is called for. Shaping such a sticky, high-hydration dough by hand is impossible. Instead, the dough is gently poured and scraped into the oiled baking pan; gravity settles it into an even layer. If you have trouble finding Castelvetrano olives, substitute any large, meaty green olive. To slice the baked focaccia for serving, use a serrated knife and a sawing motion to cut through the crust and crumb without compressing it. If desired, serve with extra-virgin olive oil for dipping. For convenience, the dough can be prepared and transferred to the baking pan a day in advance. After it has settled in the pan, cover tightly with plastic wrap and refrigerate. The next day, prepare the toppings. Uncover, top the dough with the olives and tomatoes and let stand at r