Slice the croissant in half horizontally and open both sides. Spread a little mayo and mustard on the top and bottom of the croissant.
Place a lettuce leaf on top of the bottom half, then the sliced ham, tomato slices, and another lettuce leaf on top -especially if packing for school to prevent the top croissant from soaking up the tomato juices. Close the sandwich with the top of the croissant.
Pack it for lunch:
Slice the croissant sandwich in half and place it inside a lunch container where it fits snugly, so everything stays in place.
Pack any sides, like fruits and veggies, in a separate compartment or container. Refrigerate until ready to pack inside a lunch bag, with or without an ice pack.