Rinse the sushi rice in cold water until the water runs clear. In a medium pot, combine the rinsed rice and 1½ cups of water, then bring it to a boil. Once boiling, reduce heat to low, cover, and let simmer for 15 minutes. Remove from heat, stir in 1 tablespoon of rice vinegar and ½ teaspoon of salt, and let sit covered for another 10 minutes.

In a large skillet, heat 2 tablespoons of olive oil over medium-high heat. Add the shrimp and cook for 2-3 minutes per side until opaque and pink. In a bowl, whisk together 2 tablespoons soy sauce, 1 tablespoon rice vinegar, 1 tablespoon sesame oil, 2 teaspoons sugar, and 2 tablespoons sriracha. Drizzle over the shrimp and cook for another minute.

Prepare the spicy mayo by combining ½ cup of mayonnaise with 1 tablespoon of sriracha. Mix well and adjust spiciness to taste. Set aside.

Start layering the sushi stacks using a round mold or cleaned can. Begin with a scoop of sushi rice, pressing it gently. Then, add a layer of spicy shrimp, followed by avocado and cucumber. Repeat until desired height is achieved.

Carefully lift the mold to release the sushi stacks onto a plate. Garnish with sesame seeds and cilantro or green onions. Drizzle spicy mayo over the top before serving.