Wrap the bamboo mat in plastic wrap. Using scissors, cut the full nori sheet in half to make two half sheets.
Place a half sheet of nori vertically on your bamboo mat, shiny side down, rough side facing up. Wet your fingers in water and grab sushi rice (about 2/3 cup). Spread evenly on the nori, leaving 1/2 inch at the top uncovered.
In the center of the rice, add a strip of spicy mayo, baked cauliflower, cucumber strips, sliced avocado, and shredded carrots.
To roll the sushi: Lift the edge of the bamboo mat closest to you and fold it over the filling. Hold the filling with your middle finger and apply light pressure to tighten the roll. Using your finger, wet the uncovered nori with water to act as glue. Then, lift the sushi mat and continue rolling the sushi to seal it completely. Apply gentle pressure with both hands to shape the roll.
Cut the roll into 5 pieces with a sharp, slightly wet knife. Keep the blade wet by dipping it in water before each cut and wiping it clean after each slice. Garnish with a drizzle of spicy mayo and fresh chives.