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

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

Lay out the slices of bread on a clean surface. If using butter, spread a thin layer on each slice. Spread an even layer of the cream cheese mixture onto half of the bread slices. Arrange the cucumber slices on top of the cream cheese, slightly overlapping if needed. Top with the remaining bread slices to form sandwiches.

Using a sharp knife, carefully trim the crusts off the sandwiches. Cut each sandwich into quarters or smaller rectangles for a classic tea sandwich presentation. Arrange on a platter and serve immediately.