Use a food processor and slice the cucumbers or slice very thinly by hand. Place in a colander and sprinkle with salt and allow to drain for 30 minutes. Blot with a paper towel.
Line the bread on a clean counter and butter all the slices. Lay the cucumber slices all over half of the slices of bread and sprinkle with fresh ground pepper. Top the cucumber side with bread and cut the crusts off all the sides. Cut into fourths and place on baking sheet close to one another so they don't dry out.
Place damp paper towel over bread and cover with plastic wrap and store in refrigerator.