In a large bowl, combine the yeast, lukewarm water, flour, and fine salt. Mix together with a wooden spoon or rubber spatula until a wet, shaggy dough forms. If using active dry yeast, begin by dissolving it in the warm water for 5 minutes before mixing with the other ingredients. Allow the dough to rest for 15 minutes.

Perform 3-4 sets of stretch and folds over the next hour, with about 15 minutes between each set. To do this, stretch one side of the dough up and fold it over itself, rotate the bowl, and repeat for all sides. As you continue, the dough will become stronger and less sticky. I find that not worrying too much about the timing here gives better results—just watch how your dough feels and develops.

Generously drizzle the bottom of a 9x13 inch pan with olive oil (you can also line it with parchment paper if you expect sticking). Transfer the dough into the oiled pan. Let it sit for 5-10 minutes, then, with oiled fingers, gently spread and stretch the dough out to fill the pan. If it resists, let it rest and try again in a few minutes. Allow the dough to rise in a warm place for about 1 hour, or until it has doubled in size and jiggles when you shake the pan.

Preheat your oven to 450°F (230°C). Meanwhile, slice the garlic cloves, roughly chop the sun-dried tomatoes, and chop the fresh rosemary leaves. Drizzle a little more olive oil over the surface of the risen dough. Using oiled fingers, press deep dimples all over the top of the dough. Then, press the garlic slices, sun-dried tomatoes, and rosemary into the dimples. Finally, sprinkle flaky sea salt over the top. For a more aromatic focaccia, I like to gently bruise the rosemary leaves before adding them—it releases extra oils and flavor.

Bake the focaccia in the preheated oven for 25-30 minutes, until it’s puffed, deep golden brown, and pulling away from the edges of the pan. If the sun-dried tomatoes start browning too much, loosely tent the bread with aluminum foil. Once done, let the focaccia rest in the pan for 3-4 minutes, then carefully move it to a wire cooling rack to cool further before serving. I recommend letting it cool until just warm—this gives the crumb the best texture.