01 - Dissolve the yeast and sugar in lukewarm water in a small bowl. Let stand for 10 minutes until the mixture becomes frothy and bubbly.
02 - Combine the bread flour and salt in a large mixing bowl. 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 out onto a lightly floured surface. Knead for 8–10 minutes until the dough is smooth, springy, and elastic.
04 - Transfer the dough to an oiled bowl, cover with a damp kitchen towel, and let rise in a warm spot for 1 hour or until doubled in volume.
05 - Preheat the oven to 425°F (220°C). Generously grease a 12×16 inch baking tray with olive oil.
06 - Punch down the risen dough and place it on the prepared tray. Stretch and press the dough to fill the tray, using your fingertips to create characteristic deep 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 20–30 minutes until puffy and pillowy. Bake for 20–25 minutes until the top is deep golden brown and the bottom sounds hollow when tapped.
09 - Let the focaccia cool slightly on the tray before slicing into squares. Serve warm as an appetizer, sandwich base, or alongside soups and salads.