Before expansive trade routes and adequate transportation, how did land locked areas like mongolia, or tibet, or any place far from the ocean/salt seas get salt to make things like preserving meats a common thing?
Salt is an essential nutrient; hunter-gatherers can get enough from meat, fish and shellfish to survive, but people living in an agricultural society, eating primarily grains and legumes, need supplemental salt to survive. Not too coincidentally, the mining, manufacture, and transportation of salt originated in the Neolithic Period, when agriculture was developed. [1] So, in answer to your question, "before expansive trade routes", people lived in small hunter-gatherer tribes and got their salt from eating meat, which may have been preserved in some places by drying (jerky), but otherwise had to be eaten on the spot.
Many places far from the sea have salt licks or brine springs (places where rock salt deposits reach the surface, or where underground rock salt deposits "contaminate" water). For example, Zhongba, China has brine springs and deep brine wells where salt has been made commerciallly and traded since at least 2000 B.C. [1][2] Places with sea-salt, such as the Mediterranean coast, have been drying sea salt and trading inland since antiquity; the trans-Saharan salt trade goes well back into Roman times and probably pre-dates it (note the Garamantes who controlled trans-Saharan trade in Carthaginian/Roman times) [3] In Neolithic and Bronze Age pre-historic Europe, several major settlements were founded on salt mines and salt-processing works. In pre-Columbian Mesoamerica, salt was produced on the northern coast of Yucatan and traded all over Mesoamerica and the Caribbean, including the interior Mayan Lowlands.[4] (There is also some argument for coastal Belize as the main salt-works in the region). There is also evidence of trade in salt among paleo-Indians in California.
[1] "Salt: A World History", Mark Kurlansky, http://www.worldcat.org/oclc/1004567785
[2] "Archaeological and chemical evidence for early salt production in China", Flad et al, http://www.pnas.org/content/102/35/12618.full
[3] "Money, Trade and Trade Routes in Pre-Islamic North Africa" , ed Amelia Dowler & Elizabeth R. Glavin. http://www.britishmuseum.org/pdf/Money_Trade_and_Trade_Routes_online.pdf
[4] "Archaeology and Bioarchaeology of Population Movement among the Prehispanic Maya", ed. Andrea Cucina, p 7. http://www.worldcat.org/oclc/896116844
This is not strictly about salt, but the traditional Mongol way of preserving meat is called Borts, with utilises air drying instead of salting.