01 - Rinse sushi rice under cold water until water runs clear. Combine rice and water in a pot, bring to a boil, cover, reduce heat, and simmer for 15 minutes. Remove from heat and let steam covered for 10 minutes.
02 - In a small saucepan, heat rice vinegar, sugar, and salt until dissolved. Gently fold the seasoning into the cooked rice while fanning to cool and achieve desired texture.
03 - Slice imitation crab sticks into strips and mix with Japanese mayonnaise in a small bowl.
04 - Lay a bamboo rolling mat on a clean work surface and cover with plastic wrap. Place a sheet of nori, shiny side down, on the mat. Moisten hands in a bowl of water and spread approximately 1/2 cup seasoned rice evenly over nori, leaving a 3/4 inch border at the top.
05 - Sprinkle sushi rice with tempura flakes, toasted sesame seeds, and black sesame seeds if desired. Flip the nori over so the rice is facing down.
06 - Along the lower edge of the nori, form a horizontal line with crab-mayo mixture, sliced avocado, and julienned cucumber.
07 - Using the sushi mat, roll tightly from the bottom, keeping fillings in place and pressing gently to seal the edge.
08 - With a sharp, moistened knife, slice each roll into 6 equal pieces, wiping the blade between cuts for clean edges.
09 - Top each slice with extra tempura flakes for enhanced texture.
10 - Arrange rolls on a serving dish and present with soy sauce, pickled ginger, and wasabi on the side.