Lightly crush the Red Peppercorns (1 teaspoon) and Fennel Seeds (1 teaspoon) with a mortar with pestle. Chop Fresh Rosemary (1 tablespoon) and Fresh Thyme (1 tablespoon). Mince the Garlic (2 clove).
In a small bowl combine herb rub ingredients: Freshly Ground Black Pepper (1 teaspoon), Kosher Salt (1 teaspoon), Brown Sugar (1 1/2 tablespoon), chopped rosemary and thyme, crushed red peppercorns and fennel seeds, and minced garlic.
Using a sharp knife, trim any excess fat from the Bone-in, Skin-on Chicken Thigh (1 pound). Pat chicken dry with a paper towel.
Liberally sprinkle herb rub onto both sides of chicken. Press the rub in with your fingers, so that it adheres to the chicken. Place chicken on a platter and transfer to the refrigerator to marinate for at least two hours and up to eight.
Take chicken out of the fridge 15 minutes before cooking, and preheat the grill to 375 degrees F (190 degrees C).
To grill: Place thighs skin side down for 6 minutes. To prevent flare ups and maximize the flavor of the rub, do not leave grill unattended with skin side down as the drippings can trigger a flare up that may burn the skin.
After 6 minutes, turn chicken and continue cooking for approximately 12 minutes.
For roasting, preheat the oven to 450 degrees F (230 degrees C). Set a rack over a rimmed baking sheet. Place chicken on rack. Roast for 25-30 minutes, until skin is crispy and browned and flesh is cooked through, but still juicy.
Let rest a bit before serving and enjoy!