In a large pot, add water and dried kombu. Turn the stove top on high.
Once water starts to create small bubbles, remove kombu. Bring to boil.
Turn off the heat, add bonito flakes and bring water to a boil again.
Skim off the foam from the soup if necessary.
Set a drainer in a large bowl and place paper towel over. Drain the soup carefully.
Dashi keeps for about one week in the refrigerator. If you want to keep dashi on a long term, freeze it in ice-cube trays and store the cubes in a freezer bag.
You can double or half this recipe without changing the ingredient proportions.