THE HERB TOPPING: The day before baking the flatbreads, in a medium-size bowl, mix together the sugar and salt. Chop the herbs finely, adding 1 tablespoon of the sugar-salt mixture to keep the herbs from sticking to the knife.
Add the chopped herbs and fennel seeds to the remaining sugar-salt mixture. Rub them together with your fingers to release as much of the essential oils as possible. Spread in a single layer on a sheet pan. Let dry overnight. (This will make more than you’ll need for the recipe, but the leftovers keep well in an airtight container.)
THE FLATBREAD: In a large bowl, mix ¼ cup plus 2 tablespoons of the warm water with the yeast. Set aside until the yeast dissolves and bubbles. Combine the flour and salt in a bowl, and mix well. Add the olive oil to the yeast. Mix in the flour. As the wet and dry combine, gradually add the remaining ¼ cup plus 2 tablespoons water, if needed (you may not need all of the water––you don’t want the dough to be sticky). Work in until incorporated and the dough is smooth. Cover with a clean kitchen towel. Let rest in a warm spot for 30 minutes.
Heat the oven to 450ºF. Line two 12" x 17" sheet pans with parchment paper. Pinch off pieces of the dough, each one a little larger than a golf ball. Roll each piece into a very thin 8-inch oval. Transfer two ovals of dough to each baking sheet. Brush with the glaze mixture. Sprinkle with a generous amount of the herbed sugar-salt mixture.
Bake 5 minutes; change positions of the two sheet pans top to bottom. Continue baking about 5 minutes longer or until the flatbreads puff up and are lightly caramelized on top. Keep a careful eye on them during the last few minutes of baking so the sugar doesn’t burn. After they cool, store in an airtight container, where they’ll keep for several days.