Rinse sticky rice under cold water until clear. Cook according to package instructions, typically soaking for 30 minutes and steaming for 20-25 minutes. Cool for 10-15 minutes.

Drizzle rice vinegar and sprinkle salt over cooled rice. Gently fold to combine, ensuring a fluffy and sticky texture.

Season salmon fillet with soy sauce and pepper. Cook in a medium skillet over medium heat for 3-4 minutes per side until flaky and golden. Cool slightly and flake into pieces.

Slice cucumber and avocado thinly, julienning the cucumber for even distribution.

Lay out plastic wrap on a flat surface. Spread a layer of sticky rice about 1/2 inch thick, leaving a border.

Sprinkle onion flakes and sesame seeds over rice. Layer salmon, avocado, cucumber, and scallions evenly, then drizzle with sriracha.

Use plastic wrap to roll tightly, tucking the fillings as you go. Twist ends to secure.

Let rest for 5 minutes, then slice with a sharp wet knife to preserve layers. Serve immediately.