Clean the kelp with a well wrung out damp cloth, place the kelp and bonito flakes in a container with water and let it stand overnight in fridge.
Next morning, Strain the dashi into a large bowl with a sieve lined with a kitchen paper towel.
Squeeze the dashi stock gently through the kitchen paper towel. *1
Use it for cooking or store in the fridge. *2
*1 Leftover ingredients of each different dashi stocks can be recycled to make into side dishes or condiments which is mentioned above post and also each individual dashi stock posts. *2 It will last in the fridge for a couple days. If you are not going to use it in two days, keep the dashi in the freezer. It will last about 3 months frozen.