• Use Billows and Signals to preheat your smoker to 250°F (121°C). Add the smoking wood of your choice (cherry recommended). 
• Trim the fatcap on the outside of the roast. Lamb fat carries a lot of the lamby flavor, so trim it as you like to get more or less of that taste. 
• Season the lamb on the inside (where the bone used to be) with salt, pepper, and chili. Be very liberal with the salt and with the pepper. 
• Score the fatcap with a sharp knife. Try not to cut into the meat. 
• Season the leg all over with plenty of salt. Smear the surface all over with harissa. Sprinkle black pepper onto the harissa. 
• Tie the leg up with butcher's twine to make a uniform, even roast with no bits hanging off into space. 
  
• Place the lamb on the smoker, fat-cap side down. (This will help protect the meat from any direct heat. If cooking in an offset smoker, place the lamb fat-side up.)
• Insert Signals' probe into the very center of the meat. Set the high-temp alarm for 135°F (57°C) for medium doneness. Set it lower for medium rare. 
• Close the lid and smoke the meat until the high-temp alarm sounds. (This may take 3–4 hours.)
• Verify the internal temp with Thermapen ONE. 
  

Sear the roast

• If you are searing on the same unit you were smoking on, set it up for direct-heat cooking and heat it up. If you are using another grill to sear, preheat it about halfway before removing the meat from the smoker. You want to give it a chance to cool a little while the grill comes up to heat. 
• Sear the leg of lamb on the grill over the hot flame. Rotate it every minute or so until there are some charred bits. 
  
• Move the lamb to your cutting board. 
• Slice it up and serve! This will be excellent alongside some grilled asparagus and buttered boiled new potatoes.