01 - Dissolve the yeast and sugar in lukewarm water in a small bowl. Let it stand for 10 minutes until the mixture becomes frothy and bubbly, indicating the yeast is active.
02 - In a large mixing bowl, combine the bread flour and salt. Create a well in the center and pour in the activated yeast mixture along with the olive oil.
03 - Mix until a sticky dough forms, then turn it out onto a lightly floured surface. Knead for 8 to 10 minutes until the dough becomes smooth, elastic, and springs back when pressed.
04 - Place the dough in an oiled bowl, cover with a damp kitchen towel, and let it rise in a warm spot for 1 hour or until doubled in size.
05 - Preheat the oven to 425°F. Generously grease a 12x16 inch baking tray with olive oil.
06 - Punch down the risen dough and transfer it to the prepared tray. Stretch and press the dough to fill the tray, using your fingertips to create characteristic dimples across the surface.
07 - Brush the dough generously with olive oil. Scatter chopped rosemary and flaky sea salt evenly over the surface. Arrange olives or halved cherry tomatoes if desired.
08 - Allow the shaped dough to rise for 20 to 30 minutes until puffy. Bake on the center rack for 20 to 25 minutes until the top is golden brown and the bottom sounds hollow when tapped.
09 - Remove from the oven and let the focaccia cool slightly on the tray before slicing into squares. Serve warm as a side, appetizer, or sandwich base.