In a large bowl, whisk together olive oil, minced garlic, lemon juice, oregano, salt, and pepper. Add chicken thighs and coat thoroughly. Marinate for at least 2 hours or overnight in the refrigerator.

Remove chicken from refrigerator 30 minutes before cooking to bring to room temperature.

Grate the cucumber and place in a fine-mesh strainer. Sprinkle with 1/2 teaspoon salt and let drain for 30 minutes.

Squeeze the cucumber dry using a clean kitchen towel to remove excess moisture.

In a bowl, combine Greek yogurt, drained cucumber, minced garlic, dill, lemon juice, and olive oil. Season with salt to taste. Refrigerate until ready to serve.

Preheat oven to 400°F (200°C).

Heat a large oven-safe skillet over medium-high heat. Place chicken thighs skin-side down and cook for 5-7 minutes until golden and crispy.

Flip chicken and transfer skillet to the oven. Bake for 20-25 minutes until internal temperature reaches 165°F (74°C).

Rest chicken for 5 minutes before slicing.

Bring chicken broth to a boil in a medium saucepan. Stir in couscous, remove from heat, and cover.

Let stand for 5 minutes, then fluff with a fork. Season with salt and pepper to taste.

Divide couscous among 4 bowls. Top with sliced chicken, cherry tomatoes, diced cucumber, and red onion.

Dollop generously with tzatziki and sprinkle with fresh parsley and olives if using.

Drizzle with additional olive oil and serve immediately.