In the bowl of a stand mixer combine yeast and ½ cup water. Let sit 10 minutes until yeast has dissolved and water is foamy.

Add 2 tablespoons oil, salt, ¾ cup water, and 2½ cups flour to the bowl. Fit the mixer with the dough hook and mix on medium-low speed 2 to 3 minutes, or until dough is soft and somewhat pliable. It will still be sticky. Add another 2½ cups of flour and ¾ cup water and mix on medium-low 7 minutes, or until dough is fully pliable. If still sticky, add remaining flour as needed.

Turn dough out onto a floured work surface. Knead a few times and form into a round. Grease a rimmed, 18-by-14-inch baking sheet with 2 tablespoons oil and place dough in the center. Cover with a damp towel and place in a warm, non-drafty spot (the inside of a cold oven works well) to rise for 1½ to 2 hours or until doubled in size.

Once doubled, remove towel and stretch dough to cover the entire surface of the baking sheet. It should be about ¼-inch thick. Cover again with the towel and let rise 45 minutes more.

Set a rack in the center of the oven and heat to 450°F. Using your fingertips, poke dough all over until surface is filled with divots. Press grapes, cut side down, into the divots.

Whisk together 3 tablespoons oil and 2 tablespoons water and pour over focaccia dough.

Bake 15 minutes. Sprinkle focaccia with rosemary and a few pinches of salt, rotate baking sheet, and bake another 8 to 10 minutes. Serve warm.