Wash the cucumber thoroughly using coarse salt, removing any dirt or impurities from its bumpy surface. For safety, consider using rubber gloves or carefully remove the bumpy parts with a knife!
Trim both ends of the cucumber and slice it into bite-sized pieces. To preserve its refreshing crunchiness, cut the cucumber slightly thick.
Prepare the onion, another ingredient that adds a nice crunch and sweetness to the salad, by slicing it into thin strips. To reduce its spiciness, soak the onion in a small bowl of water with 2 tbsp of vinegar for about 10 minutes.
After briefly blanching the cucumbers in boiling water with salt for 10 seconds, immediately rinse them with cold water.
After 10 minutes, drain the cucumber and onion, removing any excess water using a kitchen towel.
Now it's time to infuse the salad with flavor! Make sure you follow the order! Start by adding sugar for a refreshing touch of sweetness, followed by 1 tbsp of gochujang, 1 tbsp of soy sauce, 1 tbsp of vinegar, 1 tbsp of red pepper flakes, 0.5 tbsp of minced garlic, and finally, 2/3 tbsp of sesame oil. Mix the dressing thoroughly with the cucumber and onion until well combined. Don't forget to sprinkle some sesame seeds on top before serving for an added visual and textural delight!