Julienne the carrots.
Mix the julienned carrots with salt, sugar, and vinegar, and let them marinate for 10 minutes.
Squeeze out the moisture and season with black pepper.
Cut the baguette in half and hollow out the inside.
Spread butter on the baguette.
Layer carrot râpé, ham, cheese, and lettuce in order.
Cover with the other half of the bread to complete the sandwich.