Preheat oven to 400 degrees Fahrenheit. Mix 4 cups cooked short grain rice with 3 tbsp rice vinegar, 1 tbsp sugar, and 1 tsp salt.
Press the seasoned rice evenly into a 9x13 inch baking dish. Sprinkle the top with 1.5 tbsp furikake.
In a medium bowl, combine 8 oz flaked cooked salmon, 8 oz shredded imitation crab, 4 oz softened cream cheese, and 0.25 cup spicy mayo.
Spread the creamy seafood mixture evenly over the rice layer. Drizzle the remaining 0.25 cup spicy mayo on top. Bake in the preheated oven for 15 minutes until bubbly and golden.
Remove from oven and garnish with 1 diced avocado, 1 diced cucumber, 2 tbsp fresh green onions, and 1.5 tbsp furikake. Serve warm by scooping onto pieces of nori seaweed.