Thaw and dry the rice: Remove the frozen cauliflower rice from the bag and let it thaw at room temperature for about 5 minutes, then spread it on paper towels and gently pat dry to remove excess moisture.
Season the rice: In a large bowl, combine the thawed cauliflower rice with the seasoned rice vinegar and toasted sesame oil, tossing gently to coat evenly, about 1-2 minutes.
Taste and adjust: Add a pinch of salt if needed, keeping in mind the seasoned vinegar already carries flavor.
Slice the avocado: Cut your avocado in half lengthwise, remove the pit, and slice the flesh into thin, even strips.
Slice the cucumber: Peel the cucumber if desired, then slice it into thin batons or half-moon slices about 1/8 inch thick.
Prepare the crab: If using canned crab, drain thoroughly and break into bite-sized chunks, checking for any shell fragments.
Shred the nori: Take your nori sheet and carefully tear it into thin strips with your hands for a rustic presentation.
Dice the green onion: Slice the white and light green parts of the green onion into thin rings for garnish.
Start with rice: Divide the seasoned cauliflower rice evenly among four serving bowls, creating a small base for your toppings.
Layer the crab: Top each rice base with about 1.5 ounces of crab meat, distributing it evenly across the surface.
Arrange the vegetables: Fan the avocado slices around the crab, then add the cucumber batons in another section for a visually appealing presentation.
Garnish and sauce: Sprinkle sesame seeds and shredded nori over the bowl, drizzle with a small spoonful of mayo mixed with sriracha, and top with diced green onion.