Crumble the fresh yeast into a large mixing bowl. Add the lukewarm water, salt, olive oil, and flour.
Stir well until a thick, sticky batter-like dough forms.
Cover the bowl and let the dough rise in a warm place for about 2 to 3 hours. For a slower rise, let the dough rest overnight in the refrigerator.
Line a baking sheet with parchment paper. Transfer the dough to the baking sheet and spread it evenly with a dough scraper or spatula.
Drizzle olive oil over the top. Press small dimples into the dough with your fingertips.
Sprinkle with coarse salt.
Add toppings if desired, such as sun-dried tomatoes, olives, basil, thyme, or rosemary.
Preheat the oven to 225°C / 435°F. Let the dough rise a little more while the oven heats.
Bake on the middle rack for 25 to 30 minutes, until golden and cooked through.
Transfer the focaccia directly to a wire rack to cool.