Blocking off under the 3rd row of seats

[Silas (son of Silas)]

I would like to block off under the 3rd row of seats in my Shuttle with something that doesn't look like I've just shoved some junk it.

I don't mind if it's blocked from the front of the seat or from the boot side, I just want to stop my terrier shooting under the seat, through the boot and out of the tailgate when I open it.

Even better would be if I could somehow turn it into a storage space. Any ideas?