Rinse sushi rice under cold water until the water runs clear, then cook according to package instructions, about 18 minutes. Fold in rice vinegar and let cool.

Place a bamboo sushi mat on a clean, flat surface and position a nori sheet shiny side down. Keep a bowl of water nearby.

Wet your hands and take a handful of cooled sushi rice, spreading it evenly over the nori, leaving an inch at the top.

In the center of the rice, layer fillings like avocado, seafood, and cucumber. Avoid overfilling.

Starting from the edge closest to you, lift the bamboo mat and roll the sushi tight until sealed with water.

Slice the roll into bite-sized pieces with a damp knife, wiping the knife after each cut for clean slices.

Arrange the slices on a platter and garnish with tempura flakes. Serve with soy sauce, wasabi, and pickled ginger.