Easy Kombu Dashi Recipe
Place the dried kelp into a bottle/jar along with 3 cups of water. Leave this in the fridge overnight, or at least for 2 hours if overnight is not possible.
The next morning, pour everything into a saucepan and once it starts boiling, remove the kelp and discard it. Don't leave it in there boiling for too long or else the stock will turn slimy.
Let the stock cool and store it in the fridge once it has cooled.
This should keep for about 5 days.