Slice the cucumber, avocado, carrots, and salmon into long, thin strips. Cut the lettuce leaves into smaller pieces.
Soak a single rice paper in a shallow dish filled with warm water for 10-20 seconds. Lay it on a clean surface.
Place a portion of all the ingredients on the bottom half of the rice paper. Fold over both sides and roll it up. Repeat the process until you run out of rice papers.
Assemble the spring rolls in a single layer on a plate, making sure none of them are touching or else they will stick together.
Serve alongside peanut sauce (or any other of your favorite Asian-style dipping sauces) and enjoy!