01 - Dissolve the yeast and sugar in lukewarm water in a small bowl. Let the mixture stand for 10 minutes until it becomes frothy and bubbly on the surface.
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 everything together until a sticky dough forms. Turn out onto a lightly floured surface and knead firmly for 8 to 10 minutes, until the dough becomes smooth, springy, and elastic.
04 - Transfer the dough to a bowl coated with olive oil. Cover tightly with a damp kitchen towel and set in a warm spot for 1 hour, or until the dough has doubled in volume.
05 - Preheat the oven to 425°F (220°C). Grease a 12×16 inch (30×40 cm) baking tray generously with olive oil.
06 - Punch down the risen dough and transfer it to the prepared tray. Using your fingertips, stretch and press the dough out to fill the tray, creating deep dimples across the entire surface.
07 - Brush the dough generously with olive oil. Scatter chopped rosemary and flaky sea salt evenly over the top. Arrange olives or halved cherry tomatoes across the surface if desired.
08 - Let the topped dough rise for 20 to 30 minutes until visibly puffy. Bake on the center rack for 20 to 25 minutes until the top is deeply golden brown and the bottom sounds hollow when tapped.
09 - Allow the focaccia to cool slightly on the tray before slicing into squares. Serve warm as a standalone bread, alongside soups and salads, or sliced horizontally for sandwiches.