I had the same problem, just re use the screws and washer that are there and add a home depot washer to it.
https://www.homedepot.com/p/Everbilt-3-8-in-x-1-1-2-in-Stainless-Fender-Washer-10-Pack-39292/203436043
Installed, ordered at dealer 2 weeks ago even thought it disappered from ford accessories website.
Got tired on waiting for the Bed Mat.
Bed Tray Liner Part # NZ6Z-9900038-B
Tailgate Liner Part # NZ6Z- 9900038-C
Easy install.
Tailgate Liner was easy too.