To extract the flavors from the dried kelp and anchovies, you typically need to boil them for about 10-15 minutes. This boiling process helps create a flavorful broth or stock as the kelp and anchovies release their essence into the water. Remember, the boiling time can be adjusted slightly based on personal preference. If you desire a stronger seafood flavor, you can extend the boiling time a bit longer. However, be cautious not to overboil the ingredients, as it may lead to an overly fishy taste.