Rinse the sushi rice 2 to 3 times until the water runs clear. Drain well and cook the rice using your preferred method.
Combine the rice vinegar, sugar, and salt in a microwave-safe container. Warm the mixture for 20 to 30 seconds and stir until dissolved. Set aside.
Transfer cooked rice to a large bowl, fluff gently.
Slowly drizzle the vinegar mixture over the hot rice, mix gently until absorbed. Cover with damp towel and set aside.
Shred imitation crab meat into a bowl, mix with ½ cup Kewpie mayo. Set aside.
Mix ¼ cup Kewpie mayo with Sriracha. Transfer to squeeze bottle. Set aside.
(Optional) Combine vegetable broth, soy sauce, sugar, and mirin in saucepan. Simmer 3 to 5 minutes until glossy. Cool and transfer to squeeze bottle.
Preheat oven to 425°F.
Grease casserole pan lightly with toasted sesame or neutral oil.
Spread seasoned sushi rice evenly in pan, pressing gently.
(Optional) Sprinkle furikake over rice.
Top evenly with crab mixture, press gently.
Bake 10 to 15 minutes until heated through. Optional broil 1-2 minutes for golden top.
Remove from oven, let cool slightly.
Drizzle with spicy mayo and optional unagi sauce. Garnish with furikake.
Serve warm, scoop portions, wrap with seaweed snacks, and top with cucumber and avocado slices as desired.