I have a digital photo I am entering in an in-person photo show. I have never had to "properly" mount a digital photo before. I'm looking for some advice.

I have my frame and mat -



but the photo paper is "curling" a bit - bulging out in the center. I worry that it might touch the glass and get ruined. One solution would seem to be to glue it to the backing, but I'm reading that that is not good for the image.

Any thoughts? Most page simply say to tape it at its top edges, but that wouldn't stop the curling.

Also the frame came both with a cardboard backing as well as a square of corrugated cardboard about the size of the photo (a bit larger). Am I supposed to leave that corrugated cardboard in the layers when I arrange the final sandwich?

Thanks!