Wash cucumbers thoroughly under cold water.
Peel cucumbers using a vegetable peeler.
Slice cucumbers into thin, even rounds.
Place sliced cucumbers in large mixing bowl.
Sprinkle salt over cucumbers evenly.
Let cucumbers sit for 15 minutes.
Drain excess water from salted cucumbers.
Add rice vinegar to the bowl.
Pour sesame oil over the cucumbers.
Sprinkle sugar and chili flakes evenly.
Add minced garlic and green onions.
Toss all ingredients together gently.
Garnish with sesame seeds on top.
Chill for one hour before serving.