Score the fat cap of the lamb leg in a crosshatch pattern about 1/4-inch deep. Remove any silver skin from the exposed meat side.
Apply your chosen seasoning. For Mediterranean: combine olive oil, lemon juice, garlic, rosemary, oregano, thyme, salt, and pepper into a paste and rub all over the lamb. For Texas-style: apply coarse salt, pepper, and garlic powder generously. Wrap tightly and refrigerate for at least 4 hours or overnight.
Remove the lamb from the refrigerator 60-90 minutes before smoking to let it come to room temperature.
Preheat your smoker to 225 degrees F. Add 2-3 fist-sized cherry, apple, or pecan wood chunks.
Insert a leave-in meat thermometer probe into the thickest part of the lamb, avoiding the bone. Place the lamb fat-cap up on the smoker grate.
Smoke the lamb with the lid closed for approximately 3-4 hours (boneless) or 3.5-4.5 hours (bone-in), until the internal temperature reaches 130 degrees F for medium-rare or 140 degrees F for medium.
Optional reverse sear: remove the lamb and tent with foil. Increase smoker or grill temperature to 450-500 degrees F. Return the lamb for 10-15 minutes over indirect heat to develop a browned crust.
Rest the smoked leg of lamb for 15-20 minutes before carving. Slice against the grain in 1/2-inch slices. For bone-in, slice parallel to the bone to remove sections, then cut perpendicular to the grain.