Originally, the pieces were cut even and stapled together. Do not have an pictures. Might be more practical now to use rubber cement or silicone. The object was to get tight seal.

So does that mean it stops in bottom of folded part and stapled?TIA Dennis

Mine had Chain link fencing clips

Best Bob B

The front corners of the side and front pieces were miter cut on a 45* and hog rings connected them. In the curved rear piece with the two flaps, the outer flap was stapled to the side piece. Sorry no pictures.

I don't have pictures of the hog rings used in all four corners or details of how the
corners were cut to fit
I do have pics of a detail I've seen in three cars now.
Coincidentally all were 914 6s
All had a small blob of 'dum dum' in each corner to insure a better seal.
In the first pic the hog rings can be seen.