It seems likely to me that the marketing people are working with a third party to do that actual construction and installation of the adverts. Their options for

It seems likely to me that the marketing people are working with a third party to do that actual construction and installation of the adverts. Their options for what physical shaped plastic the advert will go in are certainly limited and there may be no option for flat plastic, or the marketers may not realize the utility of such an option. But I would be very surprised if the marketers could specify a custom shape for the plastic.