Rinse sushi rice under cold water until the water runs clear. Cook the rice with water in a rice cooker or on stovetop, bringing it to a boil, then reducing to low heat for 20 minutes. Let it rest for 10 minutes and fold in vinegar, sugar, and salt. Cool to room temperature.

Prepare your rolling area by wrapping a bamboo sushi mat in plastic wrap, and gather a bowl of water mixed with rice vinegar.

Place a sheet of nori shiny side down on the sushi mat. With wet fingers, spread cooled sushi rice over the nori, leaving a ½-inch gap at the top. Flip the nori so the rice faces down, then layer imitation crab, avocado, cucumber, and any optional fillings.

Begin rolling the sushi by tucking the edge of the mat closest to you over the filling. Roll tightly, pressing gently as you go until you reach the exposed edge of the nori, then dampen it to seal.

Carefully place the completed roll on a cutting board, seam side down. Brush with spicy mayo or eel sauce, and sprinkle with crunchy topping. Press lightly to adhere.

Using a sharp, damp knife, slice the sushi roll into 8 equal pieces. Serve with soy sauce, pickled ginger, and wasabi.