Marinate chicken breasts in BBQ sauce for at least an hour, up to 24 hours.
Marinate bacon slices in BBQ sauce for at least one hour, or overnight.
Preheat your BBQ to medium heat.
Chargrill marinated chicken breasts and bacon until cooked through and bacon is crispy.
Set aside to rest and keep warm.
In the meantime, toast bread and slice the cooked chicken.
Lather slice of bread, generously with mayonnaise, place lettuce and tomato, candied bacon, and sliced grilled BBQ chicken on top of toasted bread. Add another slice of bread spread with mayonnaise.
Continue to build your sandwich as per the first layer. Then spread the last piece of bread with mayonnaise and an extra dollop of BBQ Sauce on top. You can secure your sandwich with a skewer if desired.