Pat dry the chicken and loosen skin on breasts and thighs.
Rub chicken with olive oil, lemon zest, soy sauce, lemon juice, minced garlic, and salt. Insert lemon slices and garlic under skin, and thyme in cavity.
Mix chili flakes, paprika, cumin, remaining salt, black pepper, and thyme. Rub half over the chicken skin. Seal in a bag and refrigerate overnight or at least 4 hours.
Preheat oven to 375°F. Place potatoes in baking dish, top with chicken, and rub remaining spice blend on skin. Roast for 50-60 minutes until thigh reaches 165°F.
Brush melted butter on chicken after roasting. Rest for 15-20 minutes before carving and serving.
Notes
Ensure the chicken reaches an internal temperature of 165°F for safety.