Place the cooked sushi rice in a small bowl and fold in the rice vinegar and sea salt until evenly distributed.
Finely dice the sashimi-grade ahi tuna into small, uniform cubes.
In a separate bowl, whisk together the avocado oil mayonnaise and sriracha, then gently fold in the diced tuna.
Julienne the cucumber into thin matchsticks and slice the avocado into long, thin strips.
Place the nori sheet on a bamboo rolling mat and spread the seasoned rice across the surface, leaving a one-inch border at the top.
Arrange the spicy tuna mixture, cucumber matchsticks, and avocado slices in a horizontal line across the bottom third of the rice.
Using the bamboo mat, roll the nori tightly over the filling, applying gentle pressure to ensure a firm roll.
Use a very sharp, wet knife to slice the roll into eight even pieces and serve with coconut aminos for dipping.