Season the sushi rice with the rice vinegar, fanning and stirring until room temperature.
2. Step
On a rolling mat, place one sheet of nori with the rough side facing upwards.
3. Step
Wet your hands and grab a handful of rice and place it on the nori. Spread the rice evenly throughout the nori without mashing the rice down. Season rice with a pinch of sesame seeds, if using, then flip it over so the nori is facing upwards.
4. Step
Arrange, in a horizontal row 1 inch (2.5 cm) from the bottom, the crab followed by a row of avocado and a row of cucumber.
5. Step
Grabbing both nori and the mat, roll the mat over the filling so the extra space at the bottom touches the other side, squeezing down to make a nice tight roll. Squeeze down along the way to keep the roll from holding its shape.
6. Step
Transfer the roll onto a cutting board. Rub a knife on a damp paper towel before slicing the roll into six equal portions.
