Cork panels - making them flat ?

[outofreach]

I'm working on a new set up and want to use some of the flat cork tiles/panels from exo terra in a couple spots. Its a large set up and where I'm using tiles they will be covering a pretty big area. I bought 4 of the large pieces about 18x18 or so. My problem is I want them to attach them flat on the glass and all the tiles have the same warp to them. The warp isn't that bad but it keeps them from laying flat on the glass. So is there a secret to getting them perfectly flat on the back?

[SnakePaparazzi]

I don't have experience with them but if they are pliable enough, you could silicone them in and place something heavy to force them flat.

[JJuchems]

Submerge them in water, they float so some weight has to be applied. After about 12 hours+, gradually increase weight until desired shape is formed. This process can take several days. We this method a few times back in the days.