How can I recreate the flavour of instant ramen without the salt?
The Japanese use a stock called Dashi for the base of many soups, sauces and dishes including the famous miso soup. Dashi is made like tea by seeping several different varieties of dried ingredients such as dried bonito flakes, dried baby sardines, dried kelp and dried shitaki mushrooms in varies combinations. 

What you can do is boil water and use a teabag to seep the ingredients for a while then just remove the teabag. It requires quite a bit of bonito flakes to get any flavor. Rather than using Ramen noodles you might opt to use cellophane rice noodles or mung bean noodles instead. Finish with a dash of soy sauce, sambal or saracha. All these ingriedents can be ordered online, found at an Asian market or Whole Foods. You might also find several other types of mushrooms (watch out for sand), fish and vegetables that have been dried which will rehydrate nicely in the soup.