You may also add any other seasonings you want to the water. Place the pot over a high flame until it begins to boil. • Cooking: Add the crab legs to the boiling water. Reduce the heat to a medium setting and cook for about 6 minutes.Then remove the legs from the water and let them drain for 2 minutes. Preparation: Place 2 cups of water and 1 tablespoon of sea salt into a steamer pot. The salt adds flavor and makes the water boil faster. Place the pot over a high flame and let it come to a boil. • Cooking: Place the crab legs into a colander and set it over the boiling water.