Chicken Stock

I always feel it is a fearful waste of a chicken not to make stock from the bones.  And yesterday we had a chicken, so today:

Bones of a roast or otherwise cooked chicken - remove as much of the meat as you can, and save that to eat another time.
1-2 onions, peeled and quartered
1-2 large carrots, ditto
The green parts (the bits you usually discard) of a leek or two
A stick of celery is traditional, but we don't like the flavour of cooked celery, so we don't use that.
Lots of seasoning - salt, pepper, a couple of cloves, some mushroom ketchup, Worcestershire sauce.... whatever.  I usually add a chicken "Stock pot" gel.
Up to 2 litres boiling water

Put everything in either a slow cooker and cook on auto for about 8 hours (which is what I did) or a pressure cooker and cook on high pressure for 30 minutes.  Strain the liquid, and discard all the solids.  Use in soups, risottos, etc - or you could poach another chicken in it.....