Traveling between lands in Outward is only possible if you have at least three Travel Rations items. These are special provisions, that enable you to go to another land. To prepare them, you need two pieces of any food and one unit of salt. The food you can purchase from merchants or obtain in the process of exploring the world and the fastest and easiest method of obtaining salt is described below.
How to obtain salt?
To get salt quickly, you need a water storage item, that is, the Waterskin - you'll find it on the beach in Cierzo near the water purifying building. Now take the empty Waterskin to the source of salt water (i.e. to the beach) and fill it with salt water.
Then go to the kitchen in your house (or light a fire and set a pot on it) and place the Waterskin with salt water in the cooking menu. Now click the "Craft" button - this way you will get 5 pieces of salt as well as a Waterskin with freshwater. The process can be repeated to obtain an unlimited amount of salt.