The Smithfield ham sandwich is built around a meat so concentrated that the entire sandwich is an exercise in restraint. Smithfield ham is a dry-cured, salt-packed, long-aged Virginia country ham, dense and deeply salty, closer to a Southern answer to prosciutto than to the soft pink boiled ham of a deli case. It is sliced thin to the point of translucence, because a thick slab of meat this salty and this firm would be inedible as a sandwich. The defining decision is the slicing and the proportion: a little of this ham goes a very long way, and the build exists to carry that intensity, not to bury it.
The craft is in the cut and in what the bread is asked to do. The ham is shaved fine so it folds rather than slabs and so the salt arrives as flavor rather than as a wall. The bread is deliberately plain and soft, a white loaf or a soft biscuit, chosen to be a sweet, neutral cushion against a meat that is doing all the talking. The classic move is to dress it almost not at all: a thin film of butter or mayonnaise, and nothing acidic or assertive that would compete with the ham's cure. Where it is served on a split biscuit, the biscuit's tender, fatty crumb is the structural counter to the salt, and the sandwich is sized small on purpose, a few thin slices on a soft base, because the meat sets the limit on how much sandwich the palate wants.
The variations stay quiet, as the meat demands. A biscuit build runs the shaved ham on a hot split biscuit; a soft white-bread version keeps it cold and minimal; a sweet-and-salt build sets the ham against a smear of fig or a thin layer of honey to round the cure. The wider Virginia and Southern country-ham tradition, and the broader shelf of place-bound American specialties that travel badly and stay home on purpose, share the same logic of one defining ingredient correctly proportioned, and each of those deserves its own article rather than being crowded in here.