Combine Greek yogurt, garlic, lemon juice, olive oil, smoked paprika, oregano, salt, cumin, black pepper and red pepper flakes in a large bowl for the marinade.
Add chicken thighs to the marinade and toss to coat thoroughly.
Cover and marinate chicken for 30 minutes to 1 hour.
Prepare tzatziki by mixing Greek yogurt, dill, garlic, lemon juice, olive oil, salt, and black pepper in a bowl.
Wrap grated cucumber in paper towels or cheesecloth and squeeze out excess liquid.
Add drained cucumber to the tzatziki mixture and stir well; refrigerate until serving.
Preheat oven to 400°F and spray a baking dish with non-stick spray.
Place marinated chicken thighs in the baking dish, spoon leftover marinade on top, and bake for 20 to 22 minutes until internal temperature reaches 165°F.
Slice or dice cooked chicken.
In a bowl, combine sliced cucumbers, avocado, dill, chives, lemon juice, salt, and black pepper to make the cucumber salad.
Assemble bowls by layering cooked white rice, diced chicken, cucumber salad, tzatziki sauce, pickled red onions, cherry tomatoes, and feta cheese.
Serve with warm pita bread and enjoy.