The Mountain Men would have been without the large amounts of salt necessary to preserve meat the way house-dwelling people in towns could. They'd be doing what the Native bands would do: drying/smoking it, to make jerky, and then often going another step and turning it into pemmican. For that, the dried meat would be beaten into bits, and the fat of the animal ( usually buffalo) would be "rendered" or melted and mixed with that, as well as berries- typically blueberries or saskatoons ( berries would be a very important source of vitamins, though of course they would not know about vitamins.) Pemmican and jerky were commonly packed into a parfleche , a folding envelope or bag made of rawhide, often decorated. It would also often be two bags, which could be slung across a horse like saddlebags.

If pemmican seems rather an acquired taste now, it was the mainstay of Native communities during the long winters in the west, in the Rockies and western Canada. The North West Company would feed their employees with it. Pemmican became very much a trade item, but with the Pemmican Proclamation the NWC took control of the supply and controlled the price. There was then a Pemmican War fought over it, armed conflicts from 1815-1821 arising when the North West Company and their Red River Colony bought up large stocks of pemmican in the vicinity of its forts.

u/Bodark43 wrote an answer about the preservation of bacon in the days before refrigeration in this thread.