Chop the celery and green onions. Use a vegetable peeler to slice the cucumber and carrots into long ribbons. Thinly slice the red onion.
In a mixing bowl, stir together the mayonnaise, sriracha, salt, black pepper, toasted sesame oil, lemon juice, and sesame seeds until smooth and creamy.
Add the imitation crab meat, celery, and green onions to the bowl with the dressing. Toss gently until everything is well coated.
Arrange the cucumber ribbons, carrot ribbons, and sliced red onion on a serving platter or in small appetizer cups. Spoon the crab salad over the top.
Sprinkle with extra sesame seeds or chopped green onions if desired. Serve chilled for the freshest flavor.