Position one of the oven racks in the lowest shelf position and remove any other racks. Lay a heavy aluminum or stainless steel baking sheet, inverted (bottom-side up), on the oven rack. Turn on the oven to the highest setting, just below broil, 550°F. Place 2 large wire cooling racks on your counter, side by side. Take out your rolling pin and either a docker or a wide fork. Place a short handled oven-sweep on a small shallow baking sheet, next to the oven.
To assemble the dough, place the flour in a mixing bowl and whisk in some black pepper and the sesame seeds, if using. Stir the 2 teaspoons salt into the warm water and add this to the dry ingredients. Using your hand, mix the water and flour together, until you form a mass that leaves the sides of the bowl. Turn the mass out onto a lightly floured wooden work surface and knead the dough until smooth, 2 to 3 minutes. Using your pastry scraper, divide the dough into 14 to 16 equal pieces. Cover all the pieces while working with one at a time.
Using a rolling pin, roll out one piece of dough, as thin as possible. Never hesitate to add additional flour while rolling, to keep the dough from sticking and turn the dough over, occasionally, as you roll. When the sheet seems ultra thin, run your hand over the surface. If you detect any thicker areas, use the pin to roll over those areas until the sheet feels even. Either use a docker or a fork to prick many holes in the dough, all over. Sprinkle the top of the sheet, lightly, with more salt, then run your hand gently over the sheet to help some of the salt adhere, without pressing down.
Carefully lift the sheet, letting one side drape down as you carry it to the oven (some salt might fall off, which is fine). Open the oven and, while holding the sheet of dough at one end, fan the bottom of it, going away from you, toward the back of the oven and lay the sheet flat on the preheated (ungreased) baking sheet. Do this as quickly as possible, to prevent the oven from cooling down. Shut the oven door and set your timer for 1 minute. Meanwhile, start rolling out another piece of dough. When the timer sounds, turn the cracker over and let it bake for 45 seconds to 1 minute, checking occasionally for doneness.
When done, the crackers should be light golden and slightly blistered. (It’s not unusual for several areas to be a bit darker, due to some areas being rolled thinner than others. These darker spots are usually the best-tasting part of the cracker.) If the cracker needs a few more seconds, turn it over and shut the door. Count to 20 and check again. When satisfied, remove the cracker to a wire rack to cool. (At first the cracker will feel a bit bendable but will quickly become very crisp, as it cools). Open the oven and quickly and carefully (watch your forearms) brush any floury residue off the surface of the baking sheet, using the cool sheet to catch the crumbs. Continue rolling, baking and stacking the remaining matzos until the batch is finished. Please be aware that the oven will become progressively hotter with each sheet. So, the baking timing at end of the batch might be shorter, than at the beginning. If the matzos are baking too fast, reduce the temperature to 500°F, to gain more control.
Store the cooled matzos at room temperature stacked in sealed jumbo (2 gallon) plastic bags. If you’ve rolled the dough thin enough, the crackers will stay perfectly crisp and fresh tasting, until there’s not a crumb left. Do not store these crackers in paper bags, which makes them get stale, quickly.