Rinse cucumbers, pat dry, and slice into 1/8-inch thin rounds.

Toss cucumber slices with salt in a bowl and let sit for 10 minutes to draw out moisture.

Transfer cucumbers to a colander, rinse briefly with cold water, and press out excess liquid.

Whisk rice vinegar, soy sauce, sesame oil, sugar, garlic, and red pepper flakes in a small bowl until sugar dissolves.

Combine drained cucumbers and green onions with the dressing and toss well.

Refrigerate for at least 15 minutes to allow flavors to meld.

Toast sesame seeds in a dry skillet over medium heat for 2 minutes until golden.

Sprinkle toasted sesame seeds over the salad, toss, and serve chilled.