Prepare the spicy mayo by combining mayo, sriracha and lime juice until smooth. Store in the refrigerator until you are ready to serve.
Heat sesame oil in a skillet over medium/high heat. Saute shrimp and cauli rice for 2-3 minutes, stirring occasionally, until shrimp are pink and opaque and cauli-rice is tender. Transfer mixture to a bowl and place in the refrigerator to cool slightly while you prepare the rest of the ingredients.
Using a 1 cup dry measuring cup, layer 1/3 cup diced cucumber in an even layer at the bottom. Spread ½ of the mashed avocado on top of the cucumber. Then, fill the measuring cup up to the top with the shrimp/cauli-rice mixture.
Place your serving plate on top of the measuring cup and carefully invert the cup onto the plate. Tap the measuring cup and remove it to reveal the layered ingredients. Repeat the last step a second time to make a second sushi stack.
Drizzle the top of each sushi stack with 1 tsp liquid aminos and ½ of the spicy mayo. Garnish with nori, sesame seeds, and green onions.