Soak 4 long wooden skewers in water for 30 minutes. If using metal skewers, you don't need to soak them. If prepping the skewers ahead of time, remove the lamb from the refrigerator 30 minutes prior to grilling.
Combine the olive oil, parsley, cilantro, mint, garlic, lemon zest, lemon juice, smoked paprika, cumin, red chile flakes, coriander, and salt in a food processor or blender.
Using on/off turns, blend the mixture until it is semi-smooth. Scrape down the bowl or jar after pulsing once or twice to make sure all the ingredients are blended.
Taste the sauce/marinade and adjust the seasoning. The flavor will be sharp but will mellow and smooth out as the sauce/marinade sits.
Reserve ½ cup of the sauce/marinade to serve with the grilled kebabs.
Remove the bone from the lamb leg if using a bone-in leg of lamb. Trim the meat of excess fat and cut the lamb into 1 ½ inch cubes.
Place the lamb chunks in a large bowl and drizzle with the remaining sauce/marinade, tossing to coat. Cover the bowl with plastic wrap and refrigerate for at least 2 hours and preferably overnight. You can also store the the meat in one or two large ziploc bags in the refrigerator.
Thread the meat onto the skewers and set them aside if you haven't already done so.
Once the meat has marinated, you can skewer the meat up to 8 hours before you plan to cook it.
Heat the charcoal or gas grill to 400 degrees, or medium-high heat. Scrape the grill and, using a paper towel coated with vegetable oil, rub the grill grates with the paper towel so the kebabs don't stick.
When the fire is hot add the lamb to the grill.
Grill the kebabs for 8 - 10 minutes turning every couple of minutes until the lamb reaches an internal temperature of 145 degrees. You can use an instant-read thermometer to check the temperature. Just make sure the thermometer is not touching the skewers so that you get an accurate reading. Grilling times will vary depending on the temperature of the lamb meat and the grill. The lamb should be nice and pink inside! Be careful not to overcook the lamb.
Move the skewers to indirect heat once they are grilled to keep warm. Once all the skewers are done, remove from the grill and serve, passing the remaining sauce to drizzle over the meat.