Light the chimney starter with charcoal 30 minutes before cooking. Let it burn for 15 minutes until fully ignited.
Pour hot coals onto one side of the kettle grill. Add a few fresh coals alongside if cooking more than an hour.
Combine olive oil, crushed garlic, chili flakes, and salt in a bowl. Mix well.
Add drumsticks to a zip-lock bag and pour marinade over them. Seal and shake. Marinate 30 minutes at room temperature or overnight in the fridge.
Add cherry wood chunks to the coals just before cooking.
Wipe down the grates, then place chicken on the cooler side (indirect heat). Close the lid.
Cook at 400°F for 45 to 60 minutes, flipping every 10 to 15 minutes as needed.
Once skin is deep brown, move drumsticks directly over the coals for a 1 to 2 minute sear per side.
Remove from heat. Rest for 5 minutes before serving.