In a small bowl, stir together sour cream and 1 teaspoon dill. If desired, cut 2-1/2-inch rounds from the English muffin halves. Spread the sour cream mixture on the cut side of the toasted English muffin halves. Place cucumber slices on 2 of the English muffin halves. Sprinkle cucumbers lightly with salt. Top with remaining English muffin halves, spread side down. Slice in half to serve. (Or, for open-faced sandwiches, arrange cucumber slices over each English muffin half. If you like, garnish with additional fresh dill.) Makes 4 sandwiches.