Add orange juice, lemon juice, mustard, garlic powder, thyme, sea salt, black pepper, olive oil, and honey together in a large freezer bag.

Close the bag and shake well/squeeze to combine.

Add the leg of lamb to the bag and marinate it in the fridge overnight.

Preheat the oven to 200 degrees C/392 degrees F.

Remove the lamb from the zip lock bag and place lamb in a large baking dish or a large roasting pan without the marinade. Keep marinade at the side.

Bake the lamb for 20 minutes.

Remove the lamb from the oven after 20 minutes and reduce the heat to 140°C/284°F.

Pour 3/4 of the marinade over the lamb, cover the pan with aluminum foil or a lid if it has one, and cook for 1.5 hours.

Take the lamb out of the oven and remove the aluminum foil or lid. Carefully turn the lamb over, re-cover it with the aluminum foil or lid, and cook for another 1.5 hours.

While the leg of lamb is slow roasting, prepare your vegetables.

Take the slow-roasted leg of lamb out of the oven. Peel back the foil or lid and add the vegetables and remaining marinade to the pan.

Cook for 1 hour covered with aluminum foil.

Remove the foil or lid and cook for 30 minutes uncovered.

Check the internal temperature with a meat thermometer. I aim for 150-160°F which is medium-medium well done.

Make sure the lamb rests for 10 minutes before slicing it with a sharp knife on a cutting board. Allowing it to rest keeps the meat juicy.