Rinse the sushi rice under cold water until the water runs clear.

Combine the rice and water in a rice cooker or saucepan. Cook according to the rice cooker instructions or bring to a boil, then simmer covered for 20 minutes. Let it rest for 10 minutes.

In a small saucepan, heat rice vinegar, sugar, and salt until dissolved. Mix with the cooked rice and let it cool to room temperature.

Slice the fish into thin, rectangular pieces (about 5 cm).

Wet your hands with water, take a small amount of rice, and shape it into an oblong mound.

Optionally, add a small dab of wasabi to one side of the fish slice and press it onto the rice mound.

Place a sheet of nori shiny side down on a bamboo sushi mat.

Spread an even layer of rice over the nori, leaving 2 cm at the top edge.

Arrange fillings (cucumber, avocado, crab) in a line across the rice.

Roll the sushi tightly, using the bamboo mat to shape it. Seal the edge with a little water.

Slice the roll into 6-8 pieces with a sharp, damp knife.

Arrange nigiri and maki on a platter. Serve with soy sauce, pickled ginger, and wasabi on the side.