Dryerboxes can be for new construction or existing construction (retrofit). There are circumstances where a "New Construction" box is more appropriate than a Retrofit Dryerbox. Review numerous Customer Installed Pictures here. Also, the manufacturer of the Dryerbox offers an Online DryerBox Model Selector and a Supply House Locator.
New construction can also mean remodeling. Basically there is no drywall on the studs. These Dryerboxes have a flange that mounts to the stud (in the rough) and is installed before the drywall is hung. These Dryerboxes have a "built-in" cornerbead, and do not need a secondary trim ring.
We call these Retro-Fit units as they, in most cases, can be
installed over existing drywall. Could be considered a more difficult
installation than "new construction". If the conditions are perfect and there are no obstacles, installing a retrofit Dryerbox can save the drywall replacement work. Review numerous Customer Install Pictures here.