01 - Rinse sushi rice under cold running water until the water runs completely clear. Combine rinsed rice and 2 cups water in a medium saucepan. Bring to a rolling boil over medium-high heat, then reduce heat to low, cover tightly, and simmer for 15 minutes. Remove from heat and let rest, still covered, for 10 minutes to allow the grains to finish steaming.
02 - In a small bowl, whisk together rice vinegar, sugar, and salt until fully dissolved. Transfer the cooked rice to a large shallow bowl or baking sheet. Drizzle the vinegar mixture over the rice and gently fold it in using a rice paddle or wooden spoon, being careful not to mash the grains. Fan the rice as you fold to help it cool to room temperature and develop a glossy finish.
03 - In a small bowl, combine mayonnaise and sriracha. Stir until smooth and evenly blended. Adjust the amount of sriracha to your preferred heat level. Set aside until ready to assemble.
04 - Shred or roughly chop the imitation crab sticks. Slice the avocado. Thinly slice or julienne the cucumber and carrot, if using. Cut the nori sheets into thin strips or small squares.
05 - Divide the seasoned sushi rice among four serving bowls. Arrange the imitation crab, sliced avocado, cucumber, julienned carrot, and nori strips on top of each bed of rice. Drizzle generously with the prepared spicy mayo and sprinkle with toasted sesame seeds. Serve immediately with pickled ginger and soy sauce on the side.