In a large mixing bowl, combine the warm water, sugar, and dry yeast. Allow this mixture to sit for about 5-10 minutes until it becomes frothy.
Once the yeast is frothy, add the olive oil, salt, and flour to the bowl. Stir until a shaggy dough begins to form.
Transfer the dough to a floured surface and knead for about 10 minutes until smooth and elastic.
Place the kneaded dough in a lightly oiled bowl, cover it with a kitchen towel, and let it rise in a warm place for about 1 hour or until it has doubled in size.
While the dough rises, chop the green onions and cut the cheese into large chunks. Mix the zaatar and sumac in a small bowl.
After the dough has risen, punch it down gently to release the air. Transfer it to a baking sheet lined with parchment paper. Stretch the dough into a rectangle, about 1.5 inches thick.
Press the chunks of cheese into the surface of the dough. Sprinkle the zaatar and sumac mixture over the top, and scatter the chopped green onions.
Cover the focaccia with a kitchen towel and let it rise again for about 30 minutes. Preheat your oven to 220°C (428°F).
Once the focaccia has risen, bake it in the preheated oven for 20-25 minutes or until golden brown and crispy.
Remove the focaccia from the oven and let it cool on a rack for a few minutes. Slice and serve warm.