Heat a dry pan over medium heat and pan-fry the diced spam until the edges are browned and crisp, about 3 minutes. It renders its own fat, so no oil is needed.
In the same pan, fry or scramble the egg to your preference.
Layer the warm rice, spam, egg, and kimchi into an airtight lunch container with a well-sealed, locking lid.
Add the gochujang, sesame oil, gim, and sesame seeds on top last, so they don't get buried under the rice.
Close the lid firmly, making sure it's fully sealed, then shake the container — a real shake, holding the lid down with your hand — for about 15 seconds, until everything is tangled together into one loose, orange-tinted mix.
Open and eat straight from the container, or tip it out onto a plate.