1. In a medium bowl whisk together olive oil fresh lemon juice minced garlic dried oregano ground cumin smoked paprika kosher salt black pepper and crushed red pepper flakes if using until well combined.

2. Add the chicken thighs to the bowl or a large zip top bag and turn to coat every piece thoroughly in the marinade. Cover and refrigerate for at least 30 minutes and up to 8 hours.

3. While the chicken marinates make the tzatziki. Grate the half cucumber then squeeze out excess moisture using a clean kitchen towel or paper towels until mostly dry.

4. In a separate bowl stir together Greek yogurt grated cucumber lemon juice for tzatziki olive oil for tzatziki grated garlic chopped dill salt for tzatziki and pepper for tzatziki until smooth and creamy. Cover and refrigerate until ready to serve.

5. Prepare the toppings by chopping the lettuce dicing the tomatoes slicing the cucumber and thinly slicing the red onion. Crumble the feta cheese if using and set everything aside on a platter.

6. When ready to cook heat a grill pan outdoor grill or large skillet over medium high heat. Add the marinated chicken thighs in a single layer and cook 5 to 6 minutes per side or until nicely charred on the outside and cooked through to 165°F in the center.

7. Transfer the cooked chicken to a cutting board and let rest for 5 minutes then slice into thin strips across the grain for tender pieces that tuck easily into the pita.

8. Warm the pita or flatbreads on the grill in a dry skillet or wrapped in foil in a low oven until soft and pliable.

9. To assemble each gyro spread a generous spoonful of tzatziki down the center of a warm pita. Top with lettuce sliced chicken tomatoes cucumber red onion and a sprinkle of feta cheese if desired.

10. Drizzle with a little extra tzatziki and serve immediately with lemon wedges on the side for squeezing over the top.