Place the bamboo mat on the counter.
Place the nori, smooth side down, on the bamboo mat.
Evenly place the rice on the nori, not too thick. Leave 1 cm room on the top side, because you need this to close the roll.
Place fish and other ingredients on the rice. You can make all the combinations your heart desires. Optionally, you can also add a little bit of wasabi below the filling for a spicy taste. But watch out not to use too much, because it is very hot ;)
Use the bamboo to roll the ingredients into a nice roll. Because of the moisture, the nori will stick very well. However, if it does not stick, you can use a bit of water to secure the nori.
Use a very sharp knife to cut the roll into small pieces. Wipe the knife in-between with kitchenpaper for optimal results.