1) In a medium-sized mixing bowl (or in a bread machine set on the dough/manual cycle), combine all of the ingredients to make a very soft dough. Knead for 5 to 7 minutes (or allow the dough to go through the bread machine's dough cycle); the dough will gradually become smooth and cohesive, though it'll remain quite sticky.
2) To bake pizza immediately, divide the dough in half, and let each half rest, covered, for about 15 minutes, while you preheat your oven to 450°F. To bake pizza later, transfer the dough to a lightly greased bowl. Cover the bowl, and let the dough rise for 1 hour, then refrigerate it for up to 3 days.
3) While the dough is resting or rising (or just before you're ready to bake pizza), start preheating the oven to 450°F, and prepare your toppings.
4) For spinach and feta pizza, thaw the frozen spinach, and squeeze it in your hands (or a paper towel, or a dish towel) until it's very dry.
5) Heat the olive oil, and sauté the spinach, salt, and garlic for a couple of minutes, just until hot and well combined.
6) Divide the dough in half. You'll be working with one piece of dough at a time. To make two pizzas now, set one half aside, lightly covered, while you work with the first piece. To make one pizza now, one later, return half the dough to the refrigerator, covered; use it within a day or two.
7) Lightly grease two sheets of parchment paper, waxed paper, or (last choice) plastic wrap. Lightly grease one or two large rectangular pans (half sheet pans work well), and drizzle with olive oil.
8) Sandwich the dough between the two pieces of paper, greased sides touching the dough. Roll the dough super-thin; the low protein in Italian-style flour will allow you to do this pretty easily. If the dough fights back, walk away for 10 minutes, then return and roll some more.
9) Peel the paper off one side of the crust. Place the crust, paper side up, on the prepared pan. Peel off the remaining paper.
10) Top the crust with half the spinach and half the feta. Spray lightly with olive oil spray, if you have it; this will help the feta brown a bit.
11) Bake the pizza on a lower rack of the oven for 5 minutes, to brown the bottom crust. Then move it to a middle or upper-middle rack, and continue to bake for 10 to 15 minutes, or until the top of the crust is golden and the feta is beginning to brown.
12) Remove the pizza from the oven, and transfer it to a rack immediately, so the crust stays crisp. Serve hot.
13) Repeat with the remaining half of the dough. Or return to the refrigerator, along with the remaining topping ingredients, and bake later.
Yield: 2 large thin-crust pizzas, about 8 to 10 servings total.