some wine, chicken or beef stock, tomato juice or water
On a chopping board, pat your lamb dry with paper towels. Finely grate about half the zest off the lemon and grind into a paste with the garlic, rosemary, oil, salt and pepper using a mortar and pestle. Rub the paste all over the lamb. If you like, let it sit on the countertop for half an hour or so, or refrigerate for a few hours or overnight.
Put it into the CrockPot. Add about half a cup of liquid. Squeeze the juice of the lemon overtop too.
Cover and cook on low for 6-8 hours.