In a large bowl, stir together chicken, mayonnaise, celery, pimiento pepper, pickles, salt, and pepper.
Spread a thick layer of chicken salad onto 3 bread slices. Top each with a remaining bread slice to make 3 sandwiches.
Using a serrated bread knife in a gentle sawing motion, trim and discard crusts from sandwiches, creating a perfect square. Cut each sandwich diagonally into 4 triangles. Serve immediately, or cover with damp paper towels, place in a covered container, and refrigerate until serving time.
Notes
Make-Ahead Tip: Chicken salad can be made one day in advance, stored in a covered container, and refrigerated.
Recipe by TeaTime Magazine at https://teatimemagazine.com/pickle-and-pimento-chicken-salad-sandwiches-recipe/