Prepare the marinade: In a bowl, whisk together the garlic, salt, black pepper, oregano, dill, fennel, lemon juice, honey, olive oil, and Greek yogurt. Add the chicken thighs and stir to evenly coat the chicken. Cover and refrigerate for 3 hours.
3 cloves garlic, 1 tbsp kosher salt, ½ tsp freshly ground black pepper, 1 tsp dried oregano, ½ tsp dried dill, ½ tsp fennel seed, ⅓ cup fresh lemon juice, 1 tbsp honey, 3 tbsp olive oil, 3 tbsp Greek yogurt, 2 lb boneless skinless chicken thighs
Make the Greek salad: In a bowl, combine the tomatoes, cucumbers, onion, feta, salt, and black pepper. Stir, cover, and refrigerate until the chicken is ready to serve.
1 ½ cups quartered cherry tomatoes, 1 cup diced cucumber, ⅓ cup diced red onion, ½ cup crumbled feta cheese, ¾ tsp kosher salt, ½ tsp freshly ground black pepper
Grill the chicken: Heat the grill on high for 15 minutes. Alternatively, the chicken can be cooked on an indoor grill pan. Reduce the grill to medium-high and place the thighs on, spreading them out flat. Grill the chicken until lightly charred on both sides with an internal temperature of 165°F, 2-4 minutes per side. Remove the chicken and allow it to rest for 10 minutes to bring the internal temperature up to 170°F. Then, slice the chicken into thin strips.
Assemble: Fill each pita with chicken, tzatziki sauce, and Greek salad, and serve.