Butter one side of each side of bread and place the bread slices butter side down in the skillet or on a griddle over low heat, cook until golden brown on the bottom.
Transfer to a plate.
Stack the ham slices, then the turkey slices, and then the cheese slices in the skillet over low heat and cook until the cheese melts.
On a plate, place one piece of the bread toasted side down. Spread the BBQ sauce on the other side. Transfer the meat and cheese stack from the skillet on top of the BBQ sauce.
Add bacon slices on top. Top with tomato slices and lettuce.
Take the other slice of toast and spread the mayonnaise onto the unbuttered side and place onto the top of the sandwich, mayonnaise side down. Slice diagonally and serve.