01 - Rinse sushi rice under cold running water until the runoff becomes completely clear. Transfer the rice and 2½ cups of water to a medium saucepan, bring to a rolling boil, then cover tightly, reduce heat to low, and simmer for 15 minutes. Remove from heat and let the covered pot stand undisturbed for 10 minutes to allow the rice to steam finish.
02 - Combine rice vinegar, sugar, and salt in a small saucepan over low heat, stirring until the sugar and salt fully dissolve. Transfer the cooked rice to a large wide bowl, pour the vinegar mixture over it, and fold gently using a cutting motion while fanning the rice to bring it to room temperature. Avoid mashing the grains.
03 - Shred or cut the imitation crab sticks into thin strips. Place in a bowl and fold in the Japanese mayonnaise until evenly coated. Set aside.
04 - Place a bamboo sushi mat on your work surface and cover it with plastic wrap. Lay one sheet of nori shiny side down on the mat. Wet your hands in a bowl of water, then spread approximately ½ cup of seasoned rice evenly across the nori, leaving a ¾-inch border bare along the top edge.
05 - Scatter tempura flakes and toasted sesame seeds over the rice layer. Carefully flip the nori sheet so the rice side faces down on the plastic-wrapped mat.
06 - Arrange a horizontal line of the crab-mayonnaise mixture, sliced avocado, and julienned cucumber along the bottom edge of the nori, keeping the filling compact and even.
07 - Using the bamboo mat as a guide, roll tightly upward from the bottom edge, tucking the filling firmly as you go. Apply gentle even pressure along the roll to seal the seam. Repeat the process for the remaining three rolls.
08 - Wipe a sharp knife with a damp cloth between each cut. Slice each roll into 6 even pieces using a gentle sawing motion to maintain the shape and avoid crushing.
09 - Sprinkle additional tempura flakes over the top of each sliced piece for extra texture. Arrange on a platter and serve alongside soy sauce, pickled ginger, and wasabi paste.