Dissolve the yeast in a quarter-cup water.  Stir in the sugar and let stand until foamy (five to 10 minutes). Add the remaining water, salt, if desired, oil, and two cups flour.  Gradually add enough of the remaining flour until the mixture holds together.

On a lightly floured surface, knead the dough until smooth and elastic (10 to 15 minutes).  Place in a greased bowl, turning to coat. Cover loosely with plastic wrap or a towel and let rise until doubled in bulk (about two hours).

Punch down the dough, knead briefly, cover, and let rest for about 15 minutes.Divide into three or four equal pieces. Roll each piece into a thin round about nine inches in diameter. Sprinkle ungreased baking sheets with cornmeal or flour, place the dough rounds on top, cover, and let stand until puffy (about 30 minutes).

Preheat the oven to 425 degrees Fahrenheit (220 degrees Celsius).

Brush the tops of the dough rounds with a little oil and sprinkle with the za’atar.

Bake until lightly browned (10 to 15 minutes). Serve warm or at room temperature.