Start by lightly toasting your bread slices until they're golden and slightly crispy on the outside but still soft inside. This creates structural integrity that prevents sogginess while adding delightful texture and nutty flavor.

While the bread toasts, wash and dry your lettuce leaves thoroughly. Slice your tomatoes about one-quarter inch thick, removing excess seeds if they're particularly juicy. If using onions, slice them paper-thin and soak briefly in cold water to mellow their sharpness.

Spread mayonnaise generously on one slice of toasted bread, reaching all the way to the edges. This creates a moisture barrier that keeps your sandwich from getting soggy. On the other slice, spread a thin layer of mustard for tangy contrast.

Arrange your turkey slices in overlapping layers rather than stacking them flat. This creates pockets that hold other ingredients and gives you turkey in every bite. Use about three to four ounces of turkey per sandwich for the perfect meat-to-bread ratio.

Place your cheese slices directly on the turkey so they can slightly soften from any residual warmth. Layer crisp lettuce leaves next, followed by tomato slices seasoned lightly with salt and pepper. Add any additional toppings like avocado, pickles, or onions now.

Carefully place the top slice of bread on your beautifully layered creation. Press down gently but firmly to help everything settle together. Using a sharp serrated knife, cut diagonally from corner to corner—this isn't just traditional, it actually makes the sandwich easier to eat and looks more appealing.