You're correct that the DV448AEP has 4-way venting, and yes, one of those ways is through the bottom. It can also be vented out the back (factory default), right or left side.
For bottom or side venting, Samsung now makes the DV-1A vent kit which is available for purchase through samsungparts.com or by calling 800-627-4368. You can also click the following link for bottom venting instructions: http://tinyurl.com/yfcppzt
- Ms. Samsung