You smooth the paper to the back of the plexi and
slide it into
position as one piece. Then this piece (which is one solid piece
including the area around the keyboard) hooks onto the front bottom
of the case and drops in between the wood sides. The wood side panels
cover the ends so the plexi can't move. Then the top cover hooks
onto the front cover and drops over the back of the frame and is
held in place with screws.
And I meant to add that it is a very clever design. Much better
(more functional, easier to use) than anything OSI ever came up
with. Their look-alike, the C4P, stinks in comparison. You have
to turn the case upside down to open it, all of the components
are attached to the metal that makes up the upper surface of the
case, miserable to work on.