Combine chilli flakes, garlic, and chilli powder in a heat-proof bowl.
Heat sesame oil over medium heat in a small pan. Once the oil is hot, pour it over the chilli flakes and garlic. Mix nicely. Chilli Oil is ready. You can either store it or use it for salad.
Wash cucumbers with water and salt. Wipe with a kitchen towel.
Place them on a chopping board. Smack and smash the cucumbers using a big knife until the cucumbers start to split. Continue doing this along the length of the cucumber.
Finally, slice the cucumber diagonally. Transfer them to a bowl.
Season them with salt. Mix. Set aside 15 minutes to draw out the excess water and avoid watery salad.
Discard all the excess liquid released by the cucumbers.
Add chilli oil, salt, sugar, soy sauce, and vinegar to the cucumbers. Mix nicely
Add chopped spring onion greens, cilantro and roasted sesame seeds.
Serve smashed cucumber salad with the main course!