Place nori sheet horizontally on bamboo rolling mat with the shiny side facing the mat. With wet hands, spread about ¾ cup sushi rice evenly over the nori, leaving a ¾-inch strip on the far edge of the nori sheet free of rice. Using your finger, spread a thin stripe of wasabi horizontally along the center of the rice. Spoon about 3 tablespoons crab mixture along the center of the rice, followed by 2 to 3 avocado slices.
Rolling the bamboo mat away from you, carefully roll the nori over, leaving the rice-free strip of nori exposed.
Press the roll firmly together. Lift the top of the mat and turn the roll over so that the rice free edge of the nori overlaps the rest of the roll, sealing it.
Roll it in the mat again, pressing firmly to make sure it is sealed and shaped like a cylinder.
Using a sharp knife, carefully cut the roll into 6 pieces to serve. Repeat with remaining ingredients.