Rinse the sushi rice until the water runs clear. In a pot, combine rice with 1½ cups water; bring to a boil. Cover, reduce heat, and simmer for 15 minutes. Remove from heat, stir in rice vinegar and salt, let sit covered for 10 minutes.

Heat olive oil in a skillet over medium-high heat. Cook shrimp for 2-3 minutes on each side until opaque. Mix soy sauce, rice vinegar, sesame oil, sugar, and sriracha in a bowl; drizzle over shrimp, cooking for an additional minute.

In a bowl, combine mayonnaise and sriracha to create spicy mayo. Stir well and adjust spice level according to preference.

Begin layering sushi stacks using a round mold. Start with sushi rice at the base, followed by shrimp, avocado, and cucumber. Press each layer gently to maintain structure.

Sprinkle with sesame seeds and chopped cilantro or green onions. Drizzle spicy mayo over assembled stacks before serving.