I find the secret to that delicious, rich 'steak-like' flavour is obtained by roasting the bones (and any vegetables I'm using) in a 450 degree oven for 40 minutes before boiling them.
Today I used:
*grass fed beef bones
*garden fresh carrots
all on a baking sheet and into the oven!
Next, I put all of that (don't forget to scrape up the browned bits from the pan!) into my largest stockpot (or crockpot) along with a handful of whole peppercorns, 2 bay leaves and 2tbsps of #applecidervinegar. I cover it all with approx. 4 litres of water (I may add more later if too much water boils off), bring it to a rolling boil then turn it down to a low boil for 24 hours. (I turn the stove off before bed for safety reasons!) You can also use an Insta Pot to speed up this process to around 1 hour of cooking time.
Then I allow it to cool slightly before straining and transferring the broth to the refrigerator to cool completely, usually overnight. Then I remove the solidified fat* from the top and store the remaining deep, rich broth in jars in the fridge or glass containers in the freezer.
*don't throw out the fat! Save it for sautéing vegetables, eggs or lean meats that need a little pick-me-up! Store in the freezer for maximum shelf life.