Wash and dry the cucumber. Place it on a cutting board and cut it through its length in half. Put them next to each other with the skin op top and smash it with a cleaver to crush it. You can also use your own fists. Then cut it into diamond shaped pieces and add to a bowl.
Crush the garlic cloves on top op the cucumber.
Make the dressing by combining the vinegar with the salt and sesame oil, soy sauce and sugar. Add the chili flakes and mix it all up.
Pour the sauce over the cucumbers right before serving. Optional if you love spicy, you can drizzle extra chili oil on top.