Wash the salad and shake dry. Wash tomatoes, dab dry and cut into slices. Cut avocado in half, remove stone, peel. Cut the flesh into slices.
Cut the baguette into 4 pieces of equal size, slice open. Spread the lower halves with sauce, cover with lettuce, tomatoes, avocado and 2 roast beef slices each. Spread the rest of the sauce on top, place the upper baguette halves on top.
Arrange on a napkin.