Slow Roasted West Coast Lamb

2.25 kg / 4.5 lb leg of lamb , bone in (or shoulder) (Note 1)
Salt and pepper
1.5 tbsp olive oil
1 whole garlic head , unpeeled, cut in half horizontally
1 onion , quartered (unpeeled is fine)
2 rosemary sprigs (2 = whisper of rosemary flavour, 4 sprigs = stronger flavour)
3 cups (750 ml) beef stock/broth , low sodium
2 cups (500 ml) water
4 tbsp (50g) flour (white)
1 cup (250 ml) water
Salt and pepper , to taste
1.Slash a criss-cross pattern on both sides of the lamb and cut through the membrane about 2 mm deep.
2.Rub the lamb all over with a little olive oil and Garlic Pepper Seasoning. Rub into the leg of lamb.
3.Leave to stand at room temperature. Can be done the night before, but then refrigerate.
4.Position the oven rack one shelf below the middle and preheat the oven to 150°C. Build a platform in a roasting pan or oven safe pot with the onions, thyme, garlic and cloves. Place the prepared leg on top. Wet two lengths of baking paper long enough to hang over the sides of the pan. Cover the leg with the sheets of wet baking paper, tucking it under the lip of the pan all round, or tie it around the pan with string.
5.Place in the oven to bake slowly for ± 4½ hours.
6.Make a gravy with the pan juices, thickened a little with potato or cornflour mixed with water. Add lemon juice and a pinch of sugar, stir in a knob of butter. Taste, add a little water if too concentrated.