Slice cucumber and carrot into long strips and lightly salt them.
Drain the oil from the canned tuna, then mix well with mayonnaise, salt, and pepper.
Place a sheet of seaweed on a bamboo mat and spread the rice evenly.
Add cucumber, carrot, and tuna mayo on top of the rice.
Roll up the gimbap tightly with the fillings inside.
Cut into bite-sized pieces.