If you're using a boneless leg of lamb, you may need to use kitchen twine to tie the roast.
Make small but deep incisions in the lamb and “hide” as we say in Greece the garlic slices in them. I always think of my grandma emphasising the word “hide"...the garlic must be a surprise in your bite and you should not be able to see it. ~Tino
Rub the lamb shank or leg with salt, pepper, oregano, thyme and olive oil.
Place the lamb in a large roasting pan and pour the lemon juice over the top.
Let it marinate for at least 2 hours or in the refrigerator overnight.
Take the lamb out of the refrigerator and bring to room temperature before cooking.
Preheat oven to 400℉.
Place the lamb in the oven, covered and cook for about 20 minutes. When you can hear the oil sizzling, add the water and lower the temp to 350℉.
Cook for about 2 hours or until the lamb reaches an internal temperature of 125℉ for medium rare.
Remove lamb from the oven, place the roast on a serving platter and let rest for at least 10 minutes while it continues to cook, until the internal temperature reaches 135℉.
Slice and serve immediately, garnish with rosemary sprigs if desired.