In a medium bowl, use a fork to break the larger pieces of salmon. Add the mayo, finely chopped celery (if using), and sprinkle your favorite seasoning on top. Mix it well with a fork to incorporate all the ingredients with the mayo.
Assemble the sandwich:
Spread a little more mayonnaise on one slice of bread, just enough to coat it before you place the lettuce on top. If adding sliced tomato, place it on top of the lettuce leaf. Scoop the salmon salad on top of the lettuce and tomato, and close the sandwich with the other slice of bread.
Slice the sandwich in half and enjoy immediately or pack it for lunch.
How to pack it in a lunch box:
Place the sandwich in one compartment, and sides, like fruit and veggies, on separate compartments, keeping them away from the sandwich so it doesn't get soggy.
Pace the packed lunch inside a lunch bag and add an ice pack if necessary.