01 - Arrange the bread slices on a clean cutting board or flat surface.
02 - Spread mayonnaise evenly over all bread slices. Optionally spread Dijon mustard on two of the slices for added flavor.
03 - Place the sliced turkey breast evenly onto the two slices with mustard or the chosen base slices.
04 - Top the turkey with lettuce, tomato slices, cucumber slices, and red onion.
05 - Sprinkle salt and freshly ground black pepper over the vegetable layer.
06 - Close the sandwiches with the remaining bread slices, mayonnaise side down.
07 - Slice each sandwich in half and serve immediately.