In medieval times, people occasionally had to go for long stretches with little or no fresh meat. Instead, they relied on dried or salt-preserved meats during those times. The challenge of cooking then became to find a way for making meals interesting. Part of the reason people had to depend on preserved foods at times was the expense and difficulty in keeping animals during the winter, especially in northern Europe.
1) Dry-salting = meat or fish is buried in granular salt
Since salt was fairly expensive, generally only meats high in fat would be preserved. Mutton wasn't preserved as often since the meat is usually tough and string and was literally 'not worth its salt'.
The origins of salt-preserving food can be traced back to at least Ancient Egypt, where they used salt as part of the embalming process, as well as in food preservations. After the spread of Christianity, the business of salt-preserving fish because quite profitable, since fresh fish for the 40 days of Lent was difficult to come by for many people. Herring was the most common fish to be salted. It was essential that the herring be preserved quickly since its abundant oil tended to turn rancid within a day after the catch.
Ways of producing salt in Medieval times
1) Mining salt deposits formed from ancient seas (not very common)
Salt springs were higher in saline and didn't have extra mineral salts such as calcium and magnesium salts which you get from sea water. Of course, this made spring salts very expensive, especially since it was a limited resource. There was also a method of making salt through burning peat soaked in salt water. This produced a fine salt powder, but it was also a limited resource.
Bourgneuf Bay of Brittany produced large amounts of salt extracted from the sea, but it was coarse and of low quality, usually mixed with the remains of seaweed, sand and other contaminants. Sometimes this would make the salt a black, grey or green color. However, it was cheap. The problem with using this coarse sea salt was that it was slow to penetrate the inner parts of the meats, causing it to go bad before it was completely preserved.
Preservation by drying
This method was most often used for fish in Europe, rather than meats. It worked best with less oily fish such as cod and haddock. In cooler damp climates, this process would have required shelter from the elements and supply of fuel. The Norwegians prepared cod by exposing them to cool, crisp air and produced 'stock-fish' by the thousands. One way these would have been prepared for eating would be to pound then, then soak them in water, then cook them.