Rainbow Roll

Name: Rainbow Roll
Prep time: 10 min
Total time: 10 min
Cuisine: Japanese
Ingredients: 2/3 c. sushi rice; 2/3 c. water, plus more for rinsing; 1 (2”) piece kombu (optional); 1 tbsp. unseasoned rice vinegar; 2 tsp. sugar; Kosher salt; 2 sheets nori; 2 to 4 imitation crab sticks; 1 Persian cucumber, seeds removed and julienned; 1/2 avocado, sliced ¼” thick; 6 slices thinly sliced raw salmon (1 oz. total); 6 slices thinly sliced raw tuna (1 oz. total); 6 slices thinly sliced raw yellowtail (1 oz. total); Soy sauce, wasabi, and pickled ginger, for serving