In a large bowl, combine the flour, salt, yeast, and sugar. Add the lukewarm water and stir with a wooden spoon or your hands until a shaggy, sticky dough forms—you're not aiming for a smooth dough at this stage, just bringing everything together. Once combined, coat the surface of the dough with 3 tablespoons of olive oil, cover the bowl with plastic wrap or a kitchen towel, and refrigerate for at least 12 hours. This long, cold fermentation develops incredible flavor and gives the dough better structure for those characteristic focaccia holes.

Remove the dough from the refrigerator and let it sit at room temperature for about 15-20 minutes to take the chill off. While it warms slightly, coat a 9x13 inch baking pan generously with vegan butter and 2 tablespoons of olive oil, making sure to get into all the corners. Transfer the cold, sticky dough from the bowl into the prepared pan—it will resist at first, but gently stretch and ease it to fit, letting it relax as you go. The dough doesn't need to fill the entire pan perfectly at this point.

Cover the pan loosely with plastic wrap and let the dough rise at room temperature for 2 to 3 hours, until it's puffy and increased in volume. About 30 minutes before the dough is done rising, preheat your oven to 425°F. I like to prep the rosemary during this waiting time—strip the leaves from the stems and give them a rough chop so they're ready to scatter on top.

Once the dough has risen, remove the plastic wrap and use your fingertips to press dimples all over the surface, creating those signature focaccia indentations—press deep enough to create wells but not so hard that you deflate all the air. Drizzle the remaining 4 tablespoons of olive oil evenly over the dough, letting it pool slightly in the dimples. Scatter the chopped fresh rosemary across the top and finish with a generous sprinkle of flaky sea salt. Transfer to the preheated oven and bake for 25 to 30 minutes, until the top is golden brown and the edges are deep golden—you want real color for maximum flavor.

Remove the focaccia from the oven and let it cool in the pan for about 10 minutes. This resting period allows the crumb to set and makes it easier to slice without tearing. After cooling, you can slice it directly in the pan or transfer it to a cutting board. Serve warm or at room temperature—focaccia is wonderful either way.