Combine kombu and 8 cups water in a large saucepan. Let sit until kombu softens, 25–35 minutes. Bring to a boil over medium heat. Immediately remove from heat; fish out kombu and discard.
2
Add a splash of water to pot to cool liquid slightly. Add bonito flakes and stir once to submerge them. Return to a gentle boil, reduce heat, and simmer gently, skimming off any foam, 5 minutes. Let steep off heat, 15 minutes.
3
Strain dashi through a fine-mesh sieve or cheesecloth-lined colander into a medium bowl; do not press on solids.
