I would HIGHLY recommend sous vide for broth making.
(Actually, I would recommend sous vide as a better alterative to 80% of cooking, to be honest. It is the most used tool in my kitchen, anymore)
Generally speaking, lightly coat bones/parts/veggies in a light coat of EVOO. Roast gently in the oven. Add to sous vide bag, add water and spices, let it go at 180-200 degrees for 12 hours.
It doesn't simmer. It doesn't steam. (know how you can smell great broth cooking? You are losing flavor)
It is a near-boiling steep with 100% of nutrients and flavor locked in.
I dump the liquid into a bowl and refrigerate..... By the next morning it is the consistency of JELLO. That is when you know you got it right.
What do you use for a bag? Approximately what amount of water to amount of solids?