In a small bowl, gently fold the rice vinegar and sea salt into the warm cooked sushi rice and let it cool to room temperature.
Slice the sashimi-grade salmon into long, thin strips and slice the cooked shrimp in half lengthwise.
Julienne the cucumber into thin matchsticks and slice the avocado into thin wedges.
Place one nori sheet on a bamboo rolling mat and spread half of the rice evenly over the bottom two-thirds of the sheet.
Arrange half of the salmon, shrimp, cucumber, and avocado in a horizontal line across the center of the rice.
Using the mat, roll the nori tightly from the bottom up, lightly wetting the top edge of the nori with water to seal the roll.
Repeat the process for the second roll with the remaining ingredients.
Use a very sharp, damp knife to slice each roll into 6 to 8 even pieces.
Serve immediately with coconut aminos, wasabi paste, and pickled ginger on the side.