Rinse sushi rice under cold water until water runs clear. Combine rice and water in a saucepan and bring to a boil. Reduce heat to low, cover, and simmer for 15 minutes, or until all water is absorbed.

Remove from heat and let stand, covered, for 10 minutes. Gently fluff with a fork.

In a bowl, whisk together rice vinegar, sugar, and salt until sugar dissolves. Gently fold into the cooked rice.

In a separate bowl, combine flaked salmon, mayonnaise, and sriracha. Mix well.

Spread the rice evenly in an 8x8 inch baking dish. Top with the salmon mixture, then layer with avocado, imitation crab meat, shredded carrots, and cucumber slices.

Bake at 350°F (175°C) for 20-25 minutes, or until heated through and bubbly.

Garnish with nori seaweed squares and sesame seeds (optional) before serving.