1.Cut onion into 10cm pieces; slice pieces thinly lengthways. Place avocado and juice in small bowl; toss gently to combine.
2.Place one sheet of rice paper in medium bowl of warm water until just softened; lift sheet carefully from water, placing it on a tea-towel-covered board with a corner point facing towards you. Place one onion slice horizontally in centre of rice paper, top with a little of the avocado mixture, salmon, sprouts and coriander. Fold corner point facing you up over filling; roll rice paper sheet to enclose filling, folding in sides after first complete turn of roll. Repeat with remaining rice paper sheets and various filling ingredients.