Soak a 3” by 4” piece of dried konbu in two (US) pints of water for a few hours or overnight, then remove the konbu. You can then use it as the basis for a raw soup or stew, or make miso soup with it (not raw, but living):

Gently warm the dashi on the stove, but keep an eye on it – you don’t want to let it cook. Add any veg or reconstituted dry mushrooms you like, then stir in as much miso as you can handle! (I like it with just a little wakame & some spring onions.)

Dashi stores well in the fridge for a few days. If you still haven’t used it up, you can freeze it, though some of the subtle flavours will be lost.

Some people cut the used konbu up into thin strips & add it back into their recipe, or use it on a salad. Others just throw it away.