Peel the English cucumbers and slice into even 1-inch rounds; arrange the slices on a serving platter.
In a mixing bowl, combine the softened cream cheese, chopped fresh dill, kosher salt, and freshly ground black pepper; stir until smooth. If using, add the horseradish and mix to incorporate.
Spread a small layer of the cream cheese mixture on each cucumber round.
Top each cream-cheese–topped cucumber with a piece of smoked salmon and a small sprig of dill for garnish.
Optionally secure each appetizer with a toothpick, then chill in the refrigerator for about 10 minutes to let the flavors meld before serving.
