I have accidentally found that using a low heat setting on an iron helps one to block hats made from Raffia. On one hat that I wasn't planning on selling, I wet it, put it over my mannequin's bare head to form it. Then I let it dry and used the iron to flatten out the brim. My next experiment is to use the steam setting instead of wetting the hat. I am just about positive it will work. I'm just waiting for another hat to experiment with as the first hat looked so good I listed it for sale online.