Rinse the sushi rice under cold water until the water runs clear to remove excess starch.

Cook rice with 2 1/2 cups water in a rice cooker or on the stove following package directions. Let it rest for 10 minutes after cooking.

While the rice cooks, whisk rice vinegar, sugar, and salt in a small bowl until dissolved. Taste and adjust if you prefer sweeter or tangier rice.

Transfer cooked rice to a wide bowl. Gently fold the vinegar mixture into the rice using a cutting-and-folding motion. Fan the rice or allow it to cool to room temperature.

Place a bamboo sushi mat on a flat surface and lay one sheet of nori shiny-side down.

Wet your hands to keep rice from sticking. Grab a handful of rice (about a cup) and press it evenly over the nori, leaving a 1-inch strip at the top edge bare.

Arrange a line of shredded teriyaki chicken across the rice about 1 inch from the bottom edge. Add cucumber and avocado slices on top.

Lift the edge of the bamboo mat closest to you and fold it over the fillings, tucking gently. Roll away from you while applying even pressure to form a tight cylinder.

Dab a little water along the bare nori edge and finish rolling to seal. If the roll feels loose, press gently along the seam with the mat for 10–15 seconds.

Use a very sharp knife to slice the roll into 6–8 pieces. Clean the knife between cuts for neat slices.

Plate and serve with soy sauce and a sprinkle of sesame seeds if desired.