Prepare all ingredients. Preheat the oven to 300°F (150°C).

In a medium saucepan, bring the water to a boil. Add the rice, reduce heat to medium-low, cover, and cook until the rice absorbs the water and becomes tender, around 20 to 25 minutes.

In a small bowl, combine the rice vinegar, sugar, and salt. Gently incorporate this mixture into the warm rice, stirring lightly. Allow the rice to cool to room temperature.

Place the nori sheets on a baking sheet.

Position a nori sheet on a bamboo sushi mat, shiny side down. With wet hands, spread a thin layer of rice over the nori. Arrange a portion of the crabmeat, avocado, cucumber, and pickled ginger in a line across the center of the rice.

Using the bamboo mat, roll the nori tightly around the filling, forming a compact roll. Repeat this process with the remaining ingredients.

Slice each roll into 4 to 6 pieces using a wet, sharp knife for clean cuts. Serve and enjoy your homemade sushi.