In a bowl, mix rice vinegar, sugar, and salt until dissolved. Combine this mixture with warm sushi rice and stir gently until evenly distributed.

Spread the seasoned rice into a baking pan lined with plastic wrap, pressing down evenly. Cover and chill in the fridge for at least 4 hours or overnight.

Dice the sushi-grade salmon into small pieces. In a bowl, combine the salmon with Kewpie mayo, sriracha, soy sauce, chopped scallions, and sesame oil. Mix well and refrigerate.

Slice the chilled rice into rectangles. Heat vegetable oil in a skillet over medium heat, then fry the rice pieces until golden brown and crispy, about 3-4 minutes on each side.

On a plate, place a crispy rice rectangle. Layer with sliced avocado, a generous spoonful of the spicy salmon mixture, and jalapeno slices. Sprinkle sesame seeds on top and serve.