Shrimp Tempura Roll

Name: Shrimp Tempura Roll
Prep time: 15 min
Total time: 15 min
Cuisine: Japanese, Asian
Ingredients: 2/3 c. sushi rice; 2/3 c. water, plus more for rinsing rice; 1 (2") piece kombu (optional); 1 tbsp. unseasoned rice vinegar; 2 tsp. granulated sugar; 1/4 tsp. kosher salt; 1 qt. vegetable oil; 1/2 c. (or more) all-purpose flour; 1/3 c. (or more) water; 1 large egg; 4 jumbo shrimp (2 1/2 to 3 oz.), peeled and tails removed; 2 sheets nori; 1/2 avocado, sliced; Soy sauce, wasabi, and pickled ginger, for serving