Step 1: Brown soup bones
1-2 lbs soup bones
7qt pressure cooker
Add a dollop of canola oil and the soup bones to your pressure cooker over medium heat. Stir occasionally so the meat/bones brown.
Soup bones are usually sold as cheap extras, though you may need to specifically ask your butcher if they're not already set out. I prefer to use soup bones from grass-fed pastured cattle or bison due to their lower fat content and better lipid profile.
Pressure cookers vary greatly. I've got a 7qt Kuhn Rikon, which I love dearly. The new pressure cookers are much safer than the old ones that just had a weight set atop the lid, so get one of the newer style if you can. The Kuhn Rikon pressure cookers have multiple safety interlocks and emergency bleed valves. They can be a bit pricy, so I highly recommend checking eBay for a better deal, new or used. Replacing the gasket on a used pressure cooker makes it as good as new.
Step 2: Add vegetables
4 stalks celery
1/2 bunch parsley
Coarsely chop all of the vegetables, add to the pot, and stir.
You may use other root vegetables such as turnips and parsnips, but steer clear of any members of the cabbage family. Cabbage, cauliflower, broccoli, and the like can impart a strong bitter flavor to the stock. Beets will turn the stock a bright red/purple, so use with caution.
Step 3: Add spices
2 bay leaves
5 cloves garlic, halved
cloves (not too many; they're strong)
dried chipoltle pepper (surprisingly subtle and tasty)
allspice berries (one of my favorites)
lemongrass (the resulting stock is quite fragrant)
Add the spices of your choice and stir.