Finely chop pickled radish and boiled spinach and set aside. Mix together the black sesame seeds and soy sauce in a separate bowl.
Combine rice, sesame oil and salt and mix well. Evenly divide into four. Mix in the pickled radish, spinach, ground sesame seeds and kimchee juice, separately into each rice mixture.
Heat some oil in a frying pan and cook the beef until only half pink. Add in beef sauce ingredients and cook until done. Set aside.
Place a sheet of nori on a bamboo rolling mat. Place half of each rice mixture on top (2 centimeters wide) and repeat so you end up with 8 columns of rice. Place a sheet of plastic wrap on top and flip it over so the nori is facing up.
Place the lettuce leaves on top of the nori towards the bottom. Put the cooked beef and kimchee on top.
Using the bamboo mat and plastic wrap to help you, tightly roll everything up to create a cylinder. Using a wet knife, slice into bite-sized pieces and serve. (It's easier to cut the gimbap with the plastic wrap on)