I use my wife's clothes iron to flatten my fiber paper. I place the print face down between 2 pieces of 3 ply matt paper. The iron is set as high as it can, without steam, and then just move it up & down, left & right again, again and again until it's flat. Maybe 5 - 10 minutes. I then lay a large heavy book over the matt paper and let it cool down. I only use the matt paper for drying... nothing else. On the back sides of the matt paper I wrote down "backside only" so I don't have dirt or dust on the side that touches the fiber paper, I also store the matt paper in a bag so I don't try to use it except for flatting my print.