Drying and flattening larger fiber and RC paper

[Greg]

That works for fiber paper too?

What is „ply archival board“, sorry I am German and not a native English speaker.
Is this board similar to that what is used to make passepartouts?

Board I use is 2 ply archival board which is used for dry mounting prints on. This method works great for RC paper. As for fiber base paper, results vary. If the paper print is totally dry, works so-so. If the print still has some moisture in it but not enough to possibly stick to the archival board, this method works great. I've never had a problem with paper prints sticking to the archival board, but if the paper was moist enough, I'm sure that could happen. My darkroom now has a constant humidity level of around 50%. Repeatedly timing my drying times on the fiberglass screens (overnight usually) and then just place the prints between the archival boards for usually 24 hours just works for me.