Peel the cucumber into ornaments. Mandoline the cucumber into paper-thin rounds. Put them in a colander and sprinkle with salt, and allow the vegetables to rest for 15 minutes to extract the excess water.
The cucumbers are resting, and as they rest, prepare the herbed spread. Add the softened cream cheese, fresh dill, lemon zest, and a pinch of black pepper together in a small bowl and whip until smooth.
Dry the slices of cucumber fully with paper towels in order to make your sandwiches not wet.
Lay out the bread slices. Brush one side of all the slices with softened butter to make a waterproof coating. Spread the herbed mixture of cream cheese on top of the butter.
Place the slices of dried cucumber on half of the slices of the bread, placing them in slightly overlapping layers. Lay the remaining bread slices, spread side up.
With a sharp serrated knife, remove the crusts on all four sides. Preparing: After slicing sandwiches into three fingers (vertically), serve immediately.