Wash the lamb leg in cold water with 1/4 cup of vinegar.
Pat the lamb leg dry with paper towels.
Poke the lamb leg with a knife all around to allow the flavors to penetrate.
Rub the lamb leg with olive or vegetable oil.
Mix all the spices together, then apply them evenly over the lamb.
In the bottom of the pan, add the onion, garlic, carrot, celery, and bay leaves. Place the lamb leg on top.
Add hot water and crumble the beef bouillon cube, spreading it around the pan.
Cover the lamb with parchment paper, then add aluminum foil on top and seal tightly.
Cook in a preheated oven for 1 hour at 450°F, then reduce the temperature to 350°F and cook for another 3 hours.
After 4 hours of cooking, take the lamb out, spoon some of the juices over the meat, and enjoy!