Prepare the dough: In a large bowl, whisk together the flour, salt, and yeast. Add water and 1 tablespoon of the olive oil and use a spoon or dough whisk (I have this one) to bring it together, stirring the mixture a few times to ensure there are no unmixed pockets of flour. Cover the bowl with plastic wrap and let it rise until it doubles and moves a lot when jiggled, about 1 1/2 hours at room temperature. If you won’t need the dough until later, you can transfer it to the fridge a little before it’s fully doubled and let it finish there for a few hours or overnight

Make the focaccia: Line a 9×13-inch or rimmed baking sheet (I use these but mine are very old) with a large piece of parchment paper that extends up the sides, pressed in. Drizzle parchment with 3 tablespoons olive oil and scrape risen dough onto it. Trying to not press any air out of the dough, use your hands, sliding them underneath a little, to gently stretch the dough once or twice towards the edges. No need to make it fill out the pan completely; it will get there on its own as it rises again. If you have one, coat a second 9×13-inch or rimmed baking sheet with olive oil and upend it over the focaccia pan to act as a lid for the rise. (If you don’t have one, use another large baking dish, like a lasagna pan. The dough needs room to grow.) Set aside for another 1 1/2 hours.

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

Assemble focaccia: Heat oven to 450°F. Drain zucchini and pat it dry on paper towels. Do the same with the potatoes. Carefully remove the pan covering the focaccia dough. Do not fret if the dough looks about to spill over the sides; it’s exactly right. Cover the focaccia dough with shingles of drained zucchini and potatoes (plus salami, if using), then sprinkle with rosemary needles, to taste. Drizzle focaccia with remaining 2 tablespoons of olive oil and use your fingertips to dimple the dough several times — perhaps 20 finger impressions total. Resist over-dimpling or the focaccia becomes even, flat, and boring. Sprinkle all over with flaky sea salt.

Bake focaccia: For 30 to 38 minutes, or until a deep golden brown on top and at the edges. Keep an eye on it for the last 8 minutes and try to resist pulling it from the oven too soon. When it doesn’t brown enough, the edges soften too fast.

Transfer to a cooling rack and let cool for 5 minutes, if you can bear it. Slide the focaccia out of the pan and cut into squares [especially if you’re taking it somewhere; don’t you hate cutting up food on a picnic blanket with a plastic knife?]. Enjoy!

Leftover focaccia keeps at room temperature for a few days. Rewarming it in a 350-degree oven helps re-crisp the top.