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.