Image 1: The side panels are attached to the rear (film plane) panel and you can see the how the slots for the shutter curtain are right in front of the rear of the camera and film plane.
Image 2: Shutter test fit. You can already see how the shutter fully seals of the rear of the camera and film plane so you can safely advance the film after taking a shot.
Image 3: A different angle so you can see the shutter in the open position. Note how the window frame cutout only allows light to fall on a 35mm section of film, this protects the unexposed area of the film so there is very little waste between shots.
Image 4: With the bottom panel on and the shutter in the closed position, you can see how the shutter slips into the groove at the bottom, creating a light proof curtain so the film can be advanced and be ready for the next shot. Just to play it safe, I keep the lens cap on in between shots.
Image 5: With the top panel on and the shutter fully open you can see how the piece of wood on the shutter curtain limits the upward travel to only what is necessary to expose the film.
Image 6: With the front installed you can see how the lens opening is aligned with the 35mm frame opening on the film plane.