Place a sheet of nori, shiny side down with the long side closest to you, on a square of parchment paper (or on a bamboo sushi mat). Spoon some rice on top of the nori. Dip your fingers in water (this will help prevent the rice from sticking), then pat the rice into an even layer, going all the way to the sides but leaving a 1-inch border across the top and bottom.
Line a few julienned cucumbers horizontally across the bottom third, topped by a couple of avocado slices and some flaked salmon.
Now it’s time to roll! Hold the parchment (or sushi mat) and use it to roll the nori over the filling. The first roll should go all the way around the filling. Use the parchment to tighten the first roll, squeezing the filling into a nice compact log. Then continue rolling, using the parchment as leverage. Once you get to the end, wet the edge of the nori and seal it.
Continue with all of your rolls. Once your rolls are ready, use a sharp knife to slice them crosswise into 1-inch pieces. Serve the sushi with tamari or soy sauce for dipping, along with wasabi and pickled ginger.