This BeckerArt tip goes over how to mount/glue a sheet of watercolor paper to a panel.
PVA PH Neutral Glue https://amzn.to/3miBM4L
Hardboard panel 1/8" thick from Blick https://www.dickblick.com/items/hardb...
PVC ceiling panel 1/4" thick
https://www.menards.com/main/paint/ce...