Rinse rice under cold water until the water runs clear, about 2-3 minutes. Cook according to your rice cooker's instructions or on stovetop with 2 ¼ cups of water; bring to a boil, cover, and simmer on low for 20 minutes. Let sit covered for 10 minutes to steam, then fluff with a fork.

While rice cooks, slice avocado and cucumber into thin strips. If using imitation crab, pull it apart gently. Arrange all ingredients on a clean surface for assembly.

Lay a nori sheet on a bamboo mat, shiny side down. With wet hands, spread a thin layer of sushi rice over the nori, leaving a 1-inch border at the top. Place avocado, cucumber, and imitation crab in the center.

Starting from the bottom edge of the bamboo mat, roll the sushi tightly away from you to encase the fillings. Seal with a little water at the edge of the nori.

Sprinkle tempura flakes on top before slicing untuk added texture. Gently press to set into the sushi.

Arrange sliced rolls on a plate and serve with spicy mayo or soy sauce for dipping.