Make the marinade; combine garlic, ginger, onion, lemon juice, olive oil, cumin, paprika, salt, stock cubes, rosemary, and chili in a bowl. Blend briefly in a processor to maintain some texture.
Make 2-inch slits on the surface of the meat or goat leg. Toss the meat in half the marinade in a bowl. Reserve the remaining marinade for basting.
Massage marinade into the meat, covering the slits. Wrap in foil and marinate for 2 hours (or overnight for best results).
Remove the marinated goat meat from the fridge and allow it to come to room temperature for at least an hour. Prepare and heat the grill to high. If using a charcoal grill, cover with ashes to moderate heat.
To prevent sticking, oil a foil piece. Sear the meat on the grill for 3 minutes on each side, then transfer it to this foil. Top the meat with reserved marinade and add two more foil layers beneath, to end up with a triple layer of foil.
Place two sprigs of rosemary and the bulb of garlic on top of the goat leg. Cover the meat loosely on top with foil so it resembles a tent.
Add water to a baking tray. Lay the meat on it (Note: This helps cook the meat evenly and retains moisture). Transfer to the grill, ensuring it is at medium-low heat. Grill, turning from time to time, for 1.5 hours.
Once almost cooked, mix the honey with 2-3 tablespoons of hot water to make a glaze. Uncover meat, baste, and grill for another 15-30 minutes until browned and juices run clear.
Once cooked, transfer the meat to a tray and allow it to rest for 10-20 minutes before carving. Serve it with ugali, sukuma wiki, and kachumbari, or your favorite dishes.