Soak the vermicelli in hot water for couple of minutes. Drain and set aside.
Sprinkle mango with lemon juice.
Dip a sheet of rice paper in water, place half of lettuce leave, 1/6 of vermicelli, 1/6 of mango slices, 1 crab stick and some spinach leaves. Fold up the bottom and top border of the rice sheet, then fold sides to form a tight cylinder.
Repeat with remaining sheets of rice paper.
Transfer to a serving platter and cover with damp paper towels until ready to serve.
To prepare sauce, blend all sauce ingredients together.