01 - Place sushi rice in a fine-mesh strainer and rinse under cold running water, gently swirling with your hand, until the runoff becomes completely clear. Transfer rice and 2½ cups water to a medium saucepan. Bring to a rolling boil over high heat, then cover with a tight-fitting lid, reduce heat to low, and simmer for 15 minutes. Remove from heat and let rest, covered, for 10 minutes to allow steam to finish cooking the grains.
02 - Combine rice vinegar, sugar, and salt in a small saucepan over low heat, stirring constantly until the sugar and salt fully dissolve. Do not let the mixture boil. Remove from heat and set aside.
03 - Transfer the hot cooked rice to a large wide bowl or hangiri. Pour the warm vinegar mixture over the rice in a steady stream while gently folding and slicing through the grains with a rice paddle. Fan the rice continuously as you mix to rapidly cool it and develop a glossy finish. The rice should be at room temperature before assembling the rolls.
04 - Shred the imitation crab sticks into thin strips along the grain. Place in a bowl and fold in the Japanese mayonnaise until evenly coated. Set aside.
05 - Wrap a bamboo sushi mat tightly in plastic wrap to prevent rice from sticking. Lay one sheet of nori on the mat, shiny side facing down, with the longer edge parallel to the mat's bamboo slats. Keep a small bowl of water nearby for moistening your hands.
06 - Dip your hands in water to prevent sticking. Scoop roughly ½ cup of seasoned sushi rice and spread it evenly across the nori surface, leaving a ¾-inch bare border along the top edge. Press gently to create a uniform, thin layer without mashing the grains.
07 - Sprinkle tempura flakes and toasted sesame seeds evenly over the rice. Carefully flip the nori sheet so the rice side faces down against the plastic-wrapped mat, with the plain nori side facing up.
08 - Arrange a horizontal line of the crab-mayonnaise mixture, avocado slices, and julienned cucumber across the bottom third of the nori, about 1 inch from the bottom edge. Keep the filling compact and even for a tight roll.
09 - Lift the edge of the bamboo mat nearest you, rolling it over the filling while tucking the ingredients firmly inward with your fingertips. Continue rolling with steady, even pressure until the roll is fully sealed. Give the mat a gentle squeeze along the length of the roll to set its shape.
10 - Wet the blade of a sharp knife with a damp cloth. Slice each roll in half, then cut each half into 3 equal pieces for a total of 6 pieces per roll. Wipe and re-wet the knife between cuts for clean edges.
11 - Arrange the pieces on a serving plate cut-side up. Sprinkle additional tempura flakes over the top of each piece for extra crunch. Serve immediately with soy sauce, pickled ginger, and wasabi paste on the side.