Gently wipe the konbu with a damp cloth. Add the konbu and measured water to a pan, cover with a lid and let it stand for 8 hours or preferably overnight, so the konbu has time to release its flavour into the stock. The longer the soaking time, the more flavoursome your stock will be. At the end of the soaking time, remove the konbu from the water, add a pinch of salt an