Rinse sushi rice under cold water until clear, then cook according to package instructions. Mix in rice vinegar, sugar, and salt while warm.

Lay bamboo mat on a clean surface, place nori rough side up, and prepare small bowl of water for damp hands.

Spread sushi rice on nori, leaving an inch bare at the top.

Flip the nori so the rice is facing down toward the mat.

In the center, layer imitation crab, avocado, and cucumber. Add spicy mixture if desired.

Roll the sushi tightly from the bottom, sealing the edge with water.

Slice the roll into 6-8 equal pieces using a wet, sharp knife.

Serve with sesame seeds, soy sauce, pickled ginger, and wasabi.