One could spend the rest of their life reading threads about getting fiber papers flat, and none of them work for me at 11x14 sizes and up. Recently I tried a technique that is normally used for watercolour papers (see photo below), but the photographic papers have way too much curl, and either pop out of the gummed tape during the drying process or I end up with compound curves near the edges. I'd rather deal w/ a simple curl.
When the prints dried wavy, I then tried setting them on the counter w/ a big sheet of plywood and lots of books on top for three days. That did nothing but prevent me from reading. How DO you get these things flat? A drymount press isn't going to happen, I just want to be able to glue the prints down to a thick wood panel using archival glue, and I doubt that will hold the way they curl.