In a small bowl, combine the cream cheese, mayonnaise, dill, chives, salt, and garlic granules.
Slice the cucumber into thin, ¼-inch slices.
Cut the crust off the bread and cut in half to create rectangles.
Spread a layer of the cream cheese mixture onto the bread. Layer with 2 to 3 slices of cucumber and about ¼ cup of watercress. Close the sandwich and top with 1 cucumber slice and secure with a toothpick or sandwich pick.
Serve immediately as an appetizer or teatime snack.