Soak kombu in a deep pot of water on medium-low heat.
When the water gets close to boiling and the kombu starts to get slimy, remove it, add katsuo-bushi flakes and turn the heat up to medium. Simmer for 20 minutes or so.
Strain the katsuo-bushi out of your broth and return the liquid to the pot.
Combine 1 cup of your dashi with soy sauce, rice vinegar, mirin, apple cider vinegar and sesame oil in a mixing bowl. Let it cool in the fridge before serving your salads!