In a small bowl, gently fold the rice vinegar and sea salt into the cooked sushi rice until well combined.
Slice the sushi-grade salmon into long, thin strips approximately half an inch thick.
Julienne the cucumber into thin matchsticks and slice the avocado into thin wedges.
Place a nori sheet shiny-side down on a bamboo rolling mat.
Wet your fingers slightly and spread half of the rice in a thin, even layer over the bottom two-thirds of the nori sheet.
Arrange half of the salmon, cucumber, and avocado in a horizontal line across the center of the rice.
Using the bamboo mat, carefully roll the nori from the bottom up, keeping the tension tight to secure the fillings.
Dab the top edge of the nori with a tiny bit of water to seal the roll.
Repeat the process for the second roll.
Using a very sharp, damp knife, slice each roll into 6-8 even pieces and serve with coconut aminos, pickled ginger, and wasabi.