Rinse the short-grain white rice under cold water until the water runs clear, then cook according to package instructions, typically for 15-20 minutes. Once cooked, fold in rice vinegar while cooling.

Lay a bamboo sushi mat on a clean surface, place a sheet of nori shiny side down, and keep a bowl of vinegar-water nearby to moisten hands.

With moistened hands, scoop a handful of sushi rice and spread it evenly over nori, leaving about a 1-inch border at the top. Press gently to adhere.

Layer fillings 2 inches from the bottom of the rice-covered nori starting with imitation crab, then avocado and cucumber. Add tempura flakes if desired.

Roll the sushi by lifting the bamboo mat from the bottom, pressing inward to form a tight cylinder. Seal the edge with a little water.

Use a sharp, wet knife to slice the roll into 1-inch pieces, wiping the knife between cuts.

Serve immediately with soy sauce, pickled ginger, and wasabi for a delightful experience.