Put the flour in a large bowl. In a separate bowl, sprinkle the yeast over 1/4-cup/60 ml warm water. Stir 1/4-cup/60 g flour from the large bowl into the yeast to make a paste. Let sit until it starts to foam, about 10 minutes.
Make a well in the flour. Crack in the eggs, and add the salt, oil, and chopped rosemary. Pour in 1/4-cup/60 ml water and mix. Finally, add the yeast starter to combine, and gradually draw in the flour to make dough. Add the olives and knead into smooth dough. Place in a bowl, cover, and let rise in a warm place 1 hour.
Punch down the dough and roll into a thin rectangle, using a rolling pin. Place on a baking sheet. Cook's Note: You can scatter cornmeal underneath if you like.
Cut three slits down each side, to give the bread a leaf look. Separate the slits with your fingers to make long holes. Let the bread rise 30 minutes. Meanwhile, heat the oven to 400 degrees F.
Whisk together the egg and water, if using. Brush the top of the bread with the egg wash, then bake until risen and golden, about 25 minutes. Remove from the oven, and let cool 10 minutes at least before serving.