1. In a mortar, pound the garlic, fennel seeds, oregano and crushed red pepper with 1 1/2 teaspoons of salt until a coarse paste forms. Add the 1 1/2 tablespoons of oil.
2. Make four 2-inch slashes on the skin of each chicken leg, cutting to the bone; make 2 slashes on the underside of each leg. Rub the paste into the slashes, cover and refrigerate for 4 hours or overnight.
3. Light a grill. Brush the chicken with oil and season with salt. Grill over moderate heat, turning, until lightly charred and cooked through, 25 minutes.