Place 2 fillets sashimi-grade sea bream in a wide container and evenly sprinkle both sides with ¼ tsp salt.
Cover the container and place it in the refrigerator with one side propped up. This will allow any liquid that comes out to trickle to the bottom of the container. Rest for 1 hour.
Gently rub the surface of 2 sheets dried kelp (kombu) with a lightly dampened cloth to remove any dust or debris, then place them in a container and rub with ½ tbsp sake. Rest for 1 hour to soften.
After an hour, drain any accumulated liquid and pat the surface of the fish dry with kitchen paper.
Pat each sheet of kombu dry with kitchen paper and then sandwich the sea bream fillets between them.
Wrap with plastic wrap and rest in the refrigerator for 1 day.
Mix 1 ½ tbsp Japanese soy sauce (koikuchi shoyu) and 1 ½ tbsp dashi stock together and pour into individual dipping bowls.
Unwrap the sea bream and cut into thin slices. Discard the kombu or use it for decoration when plating up.
Serve alongside the dipping sauce and wasabi paste. Enjoy!