Rinse the sushi rice in cold water until the water runs clear. Combine the rinsed rice and water in a rice cooker and cook according to the manufacturer's instructions. While the rice is still warm, transfer it to a large mixing bowl. Add and blend in sugar, rice vinegar, and salt. Set the rice aside and let it cool.
In a mixing bowl, combine the chopped imitation crab, mayonnaise, and Sriracha sauce (you can leave without if you don't want the sushi bake spicy). Adjust the Sriracha to your preferred level of spiciness. Gently mix well.
Preheat your oven to 450°F. Brush a thin layer of oil on the baking pan. Spread an even layer of the prepared sushi rice in a baking dish (usually 9x13 inches). Then, spread half of the furikake seasoning as the second layer. Spread the imitation crab mixture evenly on top of the furikake seasoning as the third layer. Last, sprinkle the remaining furikake seasoning on the top as finishing.
Place the baking dish in the preheated oven and bake for about 15 minutes or until the top is slightly golden and the dish is heated through.
Once baked, remove the sushi bake from the oven. Garnish with chopped green onions and diced avocado. Then sprinkle roasted sesame seeds over the top. You can scoop out portions onto your plates using nori sheets or enjoy it as is. Enjoy your homemade sushi bake with imitation crab.