Been looking at this since I got my 2014... almost 10 years. I've even had discussions with WeatherTech about making some sort of a "hinged" version, if you will, of their classic cargo liner that would allow the portion that covers the rear seat to fold back over the cargo area if the rear seats are put up. In the rear seat down position (where mine have been for 10 years), it would cover the entire rear area.
I use a 3x5 industrial shop mat, with the rubber backing and the tight, short carpet. I can sweep it clean with a broom, but it obviously isn't patterned to the sides of the cargo area.
