Preheat your oven to 400°F (200°C).
In a bowl, mix lemon juice, zest, garlic, olive oil, oregano, salt, and pepper.
Place chicken thighs in a baking dish.
Pour the marinade over the chicken, ensuring it's well coated.
Allow the chicken to marinate for at least 30 minutes.
Arrange lemon slices on and around the chicken.
Bake in the preheated oven for 35-40 minutes.
Check for an internal temperature of 165°F (75°C).
Remove from oven and let it rest for 5 minutes.
Garnish with fresh rosemary and serve warm.