Rinse the sushi rice under cold water until the water runs clear.

In a medium saucepan, combine the rinsed rice and water. Bring to a boil, then reduce heat to low, cover, and simmer for 20 minutes.

Remove from heat and let it sit, covered, for 10 minutes.

In a small bowl, mix the rice vinegar, sugar, and salt until dissolved. Gently fold this mixture into the cooked rice, being careful not to mash the grains. Allow the rice to cool to room temperature.

In another bowl, combine the mayonnaise and sriracha sauce to create a spicy mayo. Adjust the sriracha to taste.

To assemble the stacks, use a round mold or a small cup. Start by layering a scoop of sushi rice at the bottom, followed by a layer of spicy shrimp, then avocado slices, and cucumber. Repeat the layers until you reach the top of the mold.

Carefully remove the mold and sprinkle the top with sesame seeds and chopped green onions. Serve with nori strips on the side if desired.