Marinate the chicken. In a bowl, whisk olive oil, lemon juice, honey, Dijon, oregano, garlic powder, salt, and pepper. Pound chicken to even thickness if needed. Coat with marinade and let sit 15–30 minutes at room temp (or up to 8 hours in the fridge).
Preheat the grill. Heat grill or grill pan to medium-high.
Oil the grates lightly to prevent sticking.
Grill the chicken. Grill 5–7 minutes per side, until the thickest part reaches 165°F/74°C. Rest on a cutting board for 5 minutes, then slice.
Mix the dressing. In a jar or small bowl, whisk olive oil, lemon juice, honey, Dijon, salt, and pepper until glossy. Taste and adjust salt or lemon.
Prep the salad base. In a large bowl, add greens, cucumber, and red onion.
Toss with about half the dressing.
Add the stars. Gently fold in watermelon, olives, and most of the feta. Sprinkle in the herbs. Add more dressing as needed; don’t drown it—watermelon releases juice.
Top and finish. Layer sliced grilled chicken on top.
Add remaining feta and nuts for crunch. Finish with a few turns of black pepper and a squeeze of lemon if you like.
Serve right away. This salad is best when the chicken is just warm and the watermelon is cold. Serve immediately for maximum contrast.