Appears Michael used a combination of a disk cutoff tool and snips to cut the dryer duct in the wall. His idea to help get the duct through the Dryerbox port is helpful. See below but he used a long wedge like piece of wood to deform the duct to assist with getting it through the port.
Possible tips to help other homeowners. Installed the Dryerbox and found a (easier) way to thread the round pipe through the oval dryerbox opening.
#6 shows a wooden 1x4 cut and tapered 4 1/2" one side and 3 3/4" inserted into downward duct to wedge/hold oval shape and slide into box. Also...I could not insert round duct into oval dryerbox until I purchased a "crimping" tool at Menards. (Worth the $18)Michael McPhearson