Start by cooking 2 cups of sushi rice according to package instructions. Once cooked, let it cool slightly and then mix in a little rice vinegar, sugar, and salt to season.
In a small mixing bowl, combine 2 tablespoons of mayonnaise with 1 1/2 tablespoons of sriracha. Adjust the amount of sriracha based on your spice preference.
Julienne the 1/2 English cucumber and slice the avocado. Shred the 5 ounces of imitation crab meat if not pre-shredded.
Lay a sheet of nori on your sushi mat, shiny side down. Wet your hands to prevent sticking and spread a thin layer of sushi rice over the nori, leaving a 1-inch border at the top.
In the center of the rice, add a line of the prepared spicy sauce, julienned cucumber, sliced avocado, and shredded crab.
Using the sushi mat, carefully lift the edge of the mat and start rolling the sushi away from you, tucking the fillings in as you go. Roll tightly but not too tight, allowing the rice to expand.
Once rolled, use a sharp knife to slice the roll into 6-8 pieces. Wet the knife with water to make cutting easier.
Sprinkle the rolls with sesame seeds and serve with soy sauce, pickled ginger, and wasabi if desired. Enjoy your homemade Spicy California Roll!