I cut the bottom "plank" to size so that there is now a 100mm overhang on either side. According to the plans, this will serve as "handles".
I also put some Ductape over the hinges and along the length of the gap just to protect the skins from the hinges or accidentally getting jammed in the gap. Might not be necessary but rather safe than sorry. ;)
Bottom part cut to size
Some Ductape to cover the hinges and close up the gap