01 - Toast all 6 slices of sandwich bread until golden brown and slightly crispy on the edges.
02 - Spread mayonnaise evenly over one side of each toasted bread slice using a butter knife.
03 - Place 2 slices of toast mayo-side up on a clean work surface. Layer each with half of the turkey or chicken breast, a slice of ham if using, 2 strips of bacon, sliced tomato, and lettuce. Season lightly with salt and pepper.
04 - Top each assembled base with a second toasted bread slice, mayo-side up. Repeat the layering with the remaining turkey or chicken, ham, bacon, tomato slices, and lettuce. Season again with salt and pepper to taste.
05 - Cap each triple-decker sandwich with the third toasted bread slice, placing it mayo-side down. Insert 2 toothpicks through each sandwich to hold the layers together, then cut diagonally into 4 wedges using a sharp knife.
06 - Arrange the sandwich quarters on a plate and serve immediately alongside potato chips, a side salad, or your preferred accompaniment.