Wash the cabbage thoroughly and shred it.
Slice the carrot and cucumber thinly.
Drain the oil from the canned tuna and prepare it.
Put rice in a bowl.
Place cabbage, carrot, cucumber, and tuna on top of the rice.
Add soy sauce, gochujang, and sesame oil, then mix everything together.
Optionally, sprinkle seaweed flakes and sesame seeds on top.