In a small bowl, combine sour cream and dill, season with salt and pepper to taste. Set the bowl aside. (This dressing can be prepared the day before the snack itself and kept in the refrigerator with the lid closed.)
Peel the cucumber and then use a vegetable peeler to cut into 16 thin slices from the pulp. Fold the cucumber slices into a small bowl and sprinkle with 1/4 teaspoon of salt, leave for 10 minutes to soften the cucumber slightly. Then blot the cucumber slices with a paper towel.
Grease the triangles of bread with sour cream sauce, and top with serpentine slices of cucumber and salmon, sprinkle the salmon sandwiches with black pepper to taste. Serve the sandwiches right away.