Rinse the sushi rice under cold water until the water runs clear.

In a pot, combine the rice and water. Bring to a boil, then reduce heat to low, cover, and cook for about 18 minutes.

Once cooked, remove from heat and let it sit, covered, for 10 more minutes.

While the rice is resting, mix rice vinegar, sugar, and salt in a small bowl. Stir until dissolved.

Transfer the rice to a large bowl and gently fold in the vinegar mixture. Let it cool to room temperature.

While the rice cools, cut your cucumber, avocado, and carrot into thin strips. If you’re using shrimp or crab, ensure it is prepared and ready to use.

Place a bamboo sushi mat on a flat surface and put a sheet of nori on top, shiny side down.

Wet your hands with water to prevent sticking, and grab a handful of sushi rice. Spread it evenly over the nori, leaving about 1 inch at the top edge.

Lay your cucumber, avocado, carrot, and optional shrimp or crab in a line across the rice.

Start rolling the sushi away from you, using the mat to help roll tightly.

Wet the top edge of the nori to seal the roll.

Use a sharp knife to slice the sushi into bite-sized pieces. Wipe the knife with a damp cloth between cuts for clean slices.

Arrange the sushi rolls on a plate and serve with soy sauce, wasabi, and pickled ginger on the side.