In a mixing bowl, combine the softened cream cheese, chopped dill, lemon juice, salt, and pepper. Mix until smooth and well combined.

Using a sharp knife or a mandoline, thinly slice the cucumber. Pat the slices dry with a paper towel to remove excess moisture if desired.

Spread a thin layer of butter on one side of each bread slice (if using). Spread a generous layer of the herbed cream cheese mixture on the unbuttered side of four bread slices. Arrange the cucumber slices evenly over the cream cheese. Top with the remaining bread slices, cream cheese side down.

Trim the crusts off the sandwiches for a clean look. Cut each sandwich into quarters or smaller rectangles. Arrange them on a platter and serve immediately.