Start by rinsing the sushi rice under cold water until it runs clear. Cook it with water, then gently fold in rice vinegar, sugar, and salt while it’s still warm. Let it cool to room temperature before rolling.
Julienne the cucumber and slice the avocado evenly. I like to keep the avocado slightly firm so it holds its shape inside the roll. You can also lightly pat the cucumber to remove extra moisture.
Place a sheet of nori shiny side down on the bamboo mat. Spread a thin layer of rice, leaving about 1 inch at the top. Lay the cucumber and avocado slices across the center and carefully roll it up using the mat for guidance.
Use a sharp, wet knife to cut the sushi roll into 6–8 pieces. Clean the knife between cuts to maintain neat edges. I find that wetting the blade slightly prevents the rice from sticking.
Arrange the rolls on a plate and serve with soy sauce, pickled ginger, and a dab of wasabi. I love drizzling a little sesame oil on top for an extra flavor boost.