For the rice base layer, mix together the rice, scallions, cucumber, carrots, crab, and spicy mayo, then season to taste with salt and pepper. If your rice mixture isn’t quite sticky enough, add a bit more mayo. Divide mixture into four and press each portion tightly into a small springform before centering it on each plate. On top of the rice base, add a layer of nori seaweed sheets. Feel free to get creative with this step – it will make your dish look very haute cuisine! Continue to build your stack with a layer of avocado slices and a layer of fish or seafood, finishing the picture with a drizzle of soy sauce.