Rinse sushi rice under cold water until the water runs clear. Combine with water in a saucepan, bring to a boil, then reduce heat and simmer for 18-20 minutes.

Transfer the cooked sushi rice to a large bowl, mix in rice vinegar, sugar, and salt while warm. Cool completely.

Combine shrimp, sriracha sauce, and mayonnaise in a bowl, mix well, and let sit for 10 minutes.

Prepare the stacking mold by using a clean stainless steel can or round mold and have it ready on a plate.

Layer sushi rice, spicy shrimp mixture, avocado slices, and cucumber slices in the mold, repeating until full.

Lift the mold to reveal the sushi stack. Sprinkle with nori strips if desired.

Serve immediately with soy sauce or extra sriracha for dipping.