There's more to stock than boiled bones. I like to add plenty of herbs, spices and vegetables to the mix. But I never salt it for fear that I will forget, and salt the dish again while cooking.
When making chicken stock I like to add 3 large carrots, a few parsnips, an onion, a bulb of garlic, and a fist full of fresh summery herbs: sage, thyme, oregano, marjoram, parsley, cilantro. I also toss in a few peppercorns.
When making beef stock, I add 3 large onions, a bulb of garlic, and some of the savory spices: a spoonful each of caraway seed, dill seed, coriander seed, a small spoon of cumin seed and peppercorns, and a few dried hot peppers (seeds included). As well as a bit of rosemary and sage.
Put your bones in a large pot and add water just to cover. I let all of the ingredients simmer for a few days on the wood stove, after all the meat and joints fall apart. Simmer long enough to cook the bones thoroughly, because you want all of the marrow and gelatin. I refresh the water level to the original amount when enough of it boils off. Some may not, but I always get a rich broth with a gelatin structure.
When using the bones of large animals you will be able to see when the marrow has been cooked out.
When my stock is ready, I skim off a majority of the fat, reserving it for other uses depending on the animal, fish out the larger bones with kitchen tongs, and filter the broth through a sieve. I pour the stock into canning jars and process them in a pressure canner. The booklet provided with my pressure canner gives the processing time as 25 minutes at 10 lbs pressure, below 10,000 ft altitude. But follow the instructions given with your own pressure canner.
After processing, when the stock is cooled to room temperature, it should be firm and gelatinous. Provided that the animal was mature and healthy. I have found that young broiler chickens do not have much gelatin or marrow in their bones, in fact, they grow so fast that their bones are easy to snap while butchering. Mature hens and older animals will make wonderful stock.