Line your bamboo sushi mat or kitchen towel with plastic wrap. Place one sheet of nori, shiny side facing down, at the top edge of the mat. Using, your finger, coat the bottom 1-inch of the nori sheet with water. Place the second sheet, shiny side down, overlapping the bottom inch of the first sheet, and press to seal.
Spread the rice on the top 2/3 of the nori, using wet fingers to press it down.
Spread the wasabi paste over the center of the rice. Place the ginger on top of the wasabi. Layer the cucumber in the center of the rice. Next to that, layer the avocado. Add the salmon next to the avocado. Sprinkle the scallion and sesame seeds over the top.
Starting at the full end, carefully roll the nori over the filling with the aid of the mat. Continue to roll tightly until all the filling is rolled up. Dampen the lower 2 inches of the nori with water, mirin, or soy sauce. Continue to roll and press the damp end over the rest of the roll.
Set the burrito aside, seam side down. Allow it to rest for a couple of minutes, then slice in half through the center with a very sharp knife or a serrated knife.
Wrap the burrito halves in parchment paper or foil and serve with soy sauce or tamari. Or, wrap again in plastic wrap and refrigerator for up to one day.