Place the dried wakame in warm water for about 5–8 minutes. It will expand several times its original size. Drain well and gently squeeze out excess water.
Slice the cucumber as thinly as possible and cut the carrot into fine strips. Thin vegetables blend better with the delicate texture of the seaweed.
Whisk together rice vinegar, soy sauce, sesame oil, sugar, and grated ginger until the sugar dissolves completely. The dressing should taste slightly sweet and tangy.
Add the soaked wakame, cucumber, carrot, and green onion to a large bowl. Pour the dressing over the salad and toss gently until everything is evenly coated.
Sprinkle toasted sesame seeds over the salad and mix lightly. If you like a little spice, add a pinch of red pepper flakes.
Cover the bowl and refrigerate the salad for at least 20 minutes. This resting time helps the seaweed absorb the delicious dressing.
Give the salad one final toss before serving. Garnish with a few extra sesame seeds and sliced green onions for a beautiful presentation.