At this point in November, I would prefer to wait to plant Boxwood until spring.
But, if you already have your boxwood purchased or need to plant this fall still, I would get them in the ground ASAP. The ground is freezing as we speak. They won't survive outdoors in a pot or B&B above ground. Just make sure they are well protected from winter burn and exposure. A sunny south face in the winter is harmful for broadleaf evergreens during the winter as the combination of sun, winter wind blasts and freeze/thaw will desiccate the leaves and stems. Boxwoods are best planted in protected spot, like an east face or a spot that is protected from the west and is shady in the afternoon.
Also be careful with watering this late in the season, as it can quickly become ice and will damage roots. Use little or no water at all this time of year, there is plenty of moisture in the ground already. Also, what water the boxwood may take up may cause more freezing problems in the plant tissues.
Good luck!
Tendril