Prep Workspace: Gather ingredients and tools including sushi rice, tuna, mayonnaise, nori sheets, a bamboo mat, and a sharp knife.

Cook Sushi Rice: Rinse sushi rice under cold water. Combine with water and bring to a boil. Reduce heat to low, cover, and simmer for 20 minutes. Let cool for 10 minutes.

Prepare Filling: Drain tuna and mix with mayonnaise and sriracha until smooth.

Assemble: Place nori on bamboo mat, spread sushi rice on top, leaving space at the top.

Add Filling: Place tuna mixture and cucumber on the rice, adding other fillings if desired.

Roll Sushi: Roll using the bamboo mat, tucking in as you go. Seal with water.

Slice: Cut the roll into 6-8 pieces using a sharp, wet knife.

Decorate: Use edible ink markers to draw designs on the sushi pieces.

Serve: Arrange on a platter with dipping sauces.