Prepare the Rice: Transfer cooked rice to a large bowl. Add 1/2 teaspoon salt and 1-2 teaspoons sesame oil. Mix well and let it cool.
Prepare the Carrot: Julienne the carrot, add a little salt, mix, and set aside to sweat.
Prepare the Spinach: Blanch spinach for 30 seconds to 1 minute. Squeeze out excess water, then season with minced garlic, salt, and sesame oil.
Prepare the Beef: Trim fat from skirt steak, slice thinly, and season with garlic, black pepper, sugar, and a little salt.
Prepare the Egg: Beat eggs with a pinch of salt. Cook in a lightly oiled pan, then cut into thin strips.
Stir-fry Carrot and Beef: Stir-fry the julienned carrot for 40 seconds. Cook the beef over medium-high heat until done.
Assemble the Gimbap: Place a sheet of seaweed on a bamboo mat, shiny side down. Spread rice thinly over the seaweed, leaving about 2 inches uncovered at the top. Arrange carrot, pickled radish, egg, spinach, and beef in the center. Roll tightly using the bamboo mat.
Serve: Cut the rolled gimbap into bite-sized pieces and serve.