Finely julienne the carrot.
Mix the julienned carrot with salt, lemon juice, and olive oil.
Let the carrot râpé marinate for about 10 minutes.
Spread sauce (e.g., mustard, mayonnaise) on the bread.
Top the bread with carrot râpé, romaine lettuce, sliced ham or cheese.
Place the other piece of bread on top to finish the sandwich.