As I guess you don’t have the exact same old scanner and printer this step is more like a rough lineout of what needs to be done and what must be cared for in special. Different scanner or printers have different mechanics but all in all they have similar structure.
I reused the bed of the scanner and its slide that contained the photo-electronics. All the electronics and glass mirrors where removed. Use a screwdriver and wear protective gloves.
So in the end just the bare plastic remained and afterwards was cut into form to have a slightly wider space for the printer head carriage which later carries the laser module with fan.