Remove excess fat from the leg and give it a massage with a nut of lard, which will then give it a nice golden color and then spread with your hands the mixture of spices and herbs with which you want to cook the leg of lamb.
Put the leg of lamb on the oven tray greased in oil, salt the meat all over its surface and place in the oven preheated to 210º C. Add the water and vinegar to the source. Let it roast for about 15-20 minutes, turning it over a couple of times to make a crust.
Then reduce the temperature to 160º C so that it cooks slowly inside during 1 hour and a half approximately. While it is roasting, during this time you will have to turn it from time to time.
After the cooking time has elapsed, we remove the leg of lamb and leave it covered for 15 minutes to finish cooking inside and recirculate the juices. Meanwhile, you can make a sauce by reducing the liquids that have remained in the roasting pan, deglazing with a few drops of vinegar.