When I first saw the illustration, I thought it was a movie camera. But according to the instruction sheet, it's a cannon.
This was another model that was impossible to build as depicted.
The long dowel holding the cannon together sticks out because the short dowel (my only other choice) can't span the 3-hole piece and secure it to the second piece. The dowel that the assembly turns on blocks the longer dowel, which is why so much of it is exposed.
The other dowel (perhaps representing the fuse?) has a different issue. The short-length dowel is too long for the box. If I were to make it almost flush with the top of the 3-hole piece, some of the dowel would be visible sticking out the bottom.
The photo below shows how close I could get to the illustrated version without altering the supplied pieces.