Preheat oven to 220C/450 F or 200C/400F with fan.

Place uncooked lamb and bones into a roasting tray and season generously with salt and pepper.  Roast in the oven for 30-45 minutes or until thoroughly browned.  You want to get it as brown as possible without burning it so use your best judgment.

After the lamb is finished roasting, transfer along with all the juices to a large pot.  Make sure that you get all the brown goodness off of the bottom of the roasting tray by pouring a cup or two of boiling water into the tray and scraping the bottom to release any bits stuck to the bottom.  Let the water sit in the tray for 5-10 minutes then pour into pot.

Add chopped leek, shallots, smashed garlic cloves, sliced ginger and coriander seeds to the pot along with the lamb.

Fill the pot up with water (about 2-3 liters/ 7-10 cups) and cook on high heat until brought to a boil.

Once at a boil, reduce heat to medium-low (or whatever heat level that keeps a steady simmer going), cover and let simmer away for 3-4 hours. You will know when the stock is ready when the meat falls off the bone and all the vegetables have turned to mush.

When stock is ready, separate the stock from the debris by running it through a sieve or strainer. Let the meat and veg debris cool before discarding it.

Let the stock cool then season with salt to taste. You may want to skim the fat off the top or do what I do and pick it off the top after it has cooled in the fridge.

Let cool completely before dividing it into portions and packaging it away in the fridge or freezer.