If using Spam, thinly slice and pan fry for a minute or two on each side over medium heat. If using leftover cooked meat, you can heat it in the microwave as necessary. If using canned tuna, press the liquid out.
Thinly slice, shave, or julienne the cucumber or carrot. You can lightly sauté the cucumber or carrot, but not necessary. If using kimchi, thinly slice and squeeze out the liquid.
Put a sheet of nori, shiny side down and shorter side towards you, on a cutting board or plate. Cut a slit to the middle of gim (seaweed sheet) from the short side.
Spread the rice evenly over the bottom left quarter of the seaweed sheet. Arrange the other ingredients on each quarter. Press lightly and tuck the filling in after each fold.