Method:
If using yogurt, drain in cheesecloth placed over a colander overnight. Discard liquid and set aside thickened yogurt.
Preheat oven to 375°F. Place pitas or flatbread in single layer on baking sheets and spread 2 teaspoons olive oil on top of bread.
Heat a heavy skillet over medium high heat. Add sesame seeds and toast, stirring often, until fragrant and golden, 2 to 3 minutes.
In small food processor, pulse marjoram, thyme, sea salt, paprika and cumin until nearly a powder, 1 to 2 minutes. Pour mixture into a small bowl and add sesame seeds. Stir to combine. Sprinkle about half the za'atar spice mixture onto pita or flatbread. If using pita, bake until crispy, about 15 minutes. If using flatbread, bake until warm, about 10 minutes.
Place labneh or yogurt in medium bowl and drizzle with remaining 1/2 teaspoon olive oil and sprinkle with za'atar to taste. Add more sea salt if desired. Serve alongside flatbread or pita and let guests tear their own and dip into labneh or yogurt.