In a stand mixer or large bowl, combine cream cheese, mayonnaise, and butter. Mix for about 3 minutes until fluffy and smooth.

Thinly slice the large seedless cucumber into uniform pieces, about a quarter inch thick.

Sprinkle kosher salt generously over the cucumber slices and let sit for about 5 minutes.

Fold green onions and celery salt into the cream cheese mixture and whip for another 2 minutes.

Generously spread the cream cheese mixture on one side of each slice of white bread.

Layer approximately four cucumber slices and a piece of butter lettuce on one slice of bread and top with another slice.

Cover the assembled sandwiches loosely with plastic wrap and refrigerate for 2 hours.

Carefully remove the crusts from each sandwich and slice diagonally or into halves.

Arrange the sliced sandwiches on a platter and serve.