Thinly slice the cucumbers into rounds, about 1/8-inch thick.
Place cucumber slices in a colander and toss with 1 teaspoon salt. Let sit for 10 minutes to draw out excess moisture.
While cucumbers rest, whisk together rice vinegar, soy sauce, sesame oil, sugar, and minced garlic in a small bowl until sugar dissolves.
Rinse the salted cucumbers under cold water to remove excess salt, then pat dry with paper towels or a clean kitchen towel.
Transfer cucumbers to a serving bowl and pour the dressing over them. Toss gently to coat evenly.
Let the salad marinate for at least 10 minutes to allow flavors to meld.
Toast sesame seeds in a dry skillet over medium heat for 1-2 minutes until fragrant and lightly golden, stirring frequently.
Sprinkle toasted sesame seeds over the salad just before serving. Add optional red pepper flakes or fresh herbs if using.