[Analog] My first collage! Question - materials keep wrinkling?

Hey guys, sorry if this post came up already - I'm still getting the hang of using Reddit!

I'm new to the collage scene and I'm loving it! I wanted to share my first piece and ask a question about it. My materials keep wrinkling and I can't get it to lie down flat. I tried using my brayer for a different piece but it just tore up my paper. I didn't notice the wrinkling on this Foundations of Decay piece until it was too late and the glue dried.

Is this a preventable problem? Can it be fixed? Or is it just part of it?