Put together the dough: In a big bowl, whisk collectively the flour, salt, and yeast. Add water and 1 tablespoon of the olive oil and use a spoon or dough whisk (I’ve this one) to convey it collectively, stirring the combination a number of occasions to make sure there are not any unmixed pockets of flour. Cowl the bowl with plastic wrap and let it rise till it doubles and strikes rather a lot when jiggled, about 1 1/2 hours at room temperature. For those who received’t want the dough till later, you possibly can switch it to the fridge just a little earlier than it’s totally doubled and let it end there for a number of hours or in a single day.

Make the focaccia: Line a 9×13-inch pan or rimmed baking sheet (I take advantage of these however mine are very outdated) with a big piece of parchment paper that extends up the edges, pressed in. Drizzle parchment with 3 tablespoons olive oil and scrape risen dough onto it. Attempting to not press any air out of the dough, use your arms, sliding them beneath just a little, to softly stretch the dough a few times in direction of the perimeters. No must make it fill out the pan fully; it would get there by itself because it rises once more. When you’ve got one, coat a second 9×13-inch pan or rimmed baking sheet with olive oil and upend it over the focaccia pan to behave as a lid for the rise. (For those who don’t have one, use one other massive baking dish, like a lasagna pan. The dough wants room to develop.) Put aside for one more 1 1/2 hours.

45 minutes to 1 hour later, put together the toppings: Place sliced zucchini in a single bowl and toss it with 1/2 teaspoon kosher salt. Put aside. Place sliced potatoes in a second bowl and toss them with 1 teaspoon kosher salt. Put aside. [This will soften the vegetables so they cook nicely.]

Assemble focaccia: Warmth oven to 450°F. Drain zucchini and pat it dry on paper towels. Do the identical with the potatoes. Fastidiously take away the pan protecting the focaccia dough. Don’t fret if the dough appears to be like about to spill over the edges; it’s precisely proper. Cowl the focaccia dough with shingles of drained zucchini and potatoes (plus salami, if utilizing), then sprinkle with rosemary needles, to style. Drizzle focaccia with remaining 2 tablespoons of olive oil and use your fingertips to dimple the dough a number of occasions — maybe 20 finger impressions complete. Resist over-dimpling or the focaccia turns into even, flat, and boring. Sprinkle throughout with flaky sea salt.

Bake focaccia: For 30 to 38 minutes, or till a deep golden brown on high and on the edges. Regulate it for the final 8 minutes and check out to withstand pulling it from the oven too quickly. When it doesn’t brown sufficient, the perimeters soften too quick.

Switch to a cooling rack and let cool for five minutes, in the event you can bear it. Slide the focaccia out of the pan and reduce into squares [especially if you’re taking it somewhere; don’t you hate cutting up food on a picnic blanket with a plastic knife?]. Get pleasure from!

Leftover focaccia retains at room temperature for a number of days. Rewarming it in a 350-degree oven helps re-crisp the highest.