Put the water in a pot and add the kombu to soak for at least half an hour up to 4 hours
Place the pot on medium low heat and heat to about 190° - steamy but not boiling. This should take 20-30 minutes. This step extracts the umami from the kelp. DO NOT LET IT BOIL
Remove the kombu
Add the bonito flakes. Simmer for about 10 minutes. The bonito will sink to the bottom of the pot.
Strain through a fine mesh sieve