pick some bones and meat of your choice. Bones are important for flavour esp if the meat you choose is very lean. Duh. low cal.
-this would work with a chicken or turkey carcass too - not just red meat. I've also done it with roasts that weren't going to be eaten. Convenient in that it can be frozen, and it can sit in the fridge for a week and be fine. Tastes better the longer it sits.

-in a big pot of cold water put bones, meat, celery root, some carrots, a leek and some bay leaves. Let sit for a long time. You can substitute onion for leek..
-on the lowest possible heat let the stuff just go.. overnight, all the next day... turn it off. let it cool.
-take out the veggies and discard. I sometimes put the carrots back in. Separate meat from bone.. add parsley and simmer for a while longer. Eat.. or to make even lower fat chill first, take the fat off the top then eat.
I usually put some boullion in at the end just for the saltiness.