1) To make the starter: Mix the water and 1/16 teaspoon yeast, then add the flour, stirring until the flour is incorporated. The starter will be paste-like; it won't form a ball.
2) Cover and let rest at room temperature for about 14 hours; the starter will be bubbly. If you make this in the late afternoon, it'll be ready to go by the next morning.
3) Combine the risen starter with the remaining dough ingredients, and mix and knead — by hand, mixer, or bread machine set on the dough cycle — to make a soft, smooth dough. If you're kneading in a stand mixer, it should take about 7 minutes at second speed.
4) Place the dough in a lightly greased container, cover, and let it rise for 1 hour.
5) Gently deflate the dough, and allow it to rise for another hour; it should have doubled in bulk from its original volume.
6) Sometime during the dough's rise, prepare the vegetables. Trim the zucchini, and slice about 3/4" thick. Toss with olive oil; sprinkle with Pizza Seasoning (or other dried herbs), if desired. Spread the zucchini, in a single layer, on a lightly greased baking sheet.
8) Cut the cherry tomatoes in half. Toss them with olive oil and Pizza Seasoning or dried herbs. Place them, cut-side down, on a lightly greased baking sheet. Cut the scallions into 2" to 3" pieces. Toss in oil, sprinkle with herbs, and place on the baking sheet along with the tomatoes.
7) Place the vegetables in a preheated 400°F oven. Bake the zucchini, turning it over once, until it's golden brown. This will take about 60 minutes. Bake the scallions and tomatoes until they're starting to brown and soften, about 25 to 30 minutes.
8) Remove the vegetables from the oven, use a spatula to gently loosen them from the pan, and set them aside.
9) Lightly grease an 18" x 13" rimmed baking sheet (half-sheet pan) with non-stick vegetable oil spray. Drizzle olive oil atop the spray; the spray keeps the bread from sticking, while the olive oil gives the bottom crust great crunch and flavor.
10) Gently deflate the dough. Pull and shape it into a rough rectangle, and pat it into the pan. As soon as it begins to fight you and shrink back, stop patting. Wait 15 minutes; pat the dough farther towards the edges of the pan. Repeat once more, if necessary, until the dough is close to covering the bottom of the pan.
11) Place the zucchini atop the dough. Cover the pan, and allow the dough to rise until it's very puffy, almost billowy. This will take about 2 to 3 hours. Toward the end of the rising time, preheat the oven to 425°F.
12) Place the pan on a lower rack in your oven, and bake the focaccia for 15 minutes. Remove the pan from the oven, top with the scallions and tomatoes, return to the oven, and bake for an additional 10 minutes, until the crust around the edges (and showing between the vegetables) is golden brown.
13) Remove the focaccia from the oven, and top with Parmesan cheese, if desired.
Yield: one focaccia, 8 to 10 servings.