The perspex is screwed into the recess underneath the top. The LCD screen is not pressed up hard against the perspex as the pressure effected the display with my particular screen. The LCD is attached to 2 wooden struts underneath so the screen sits just below the perspex.
Holes were drilled for the joystick, 2 buttons on top and the one player, two player buttons on the side.
Wooden tabs are added around the bottom edge for attaching covers made of 4mm ply wood made from the back of old cupboards. There is one large cover for the main section and one small cover for the joystick and buttons section.
This photo shows a double adapter used to power the raspberry pi and the LCD screen. One black cable exits through the cover down the side of one leg. The double adapter was changed to a 4 port adapter later when I added sound.