I have flattend the buckram by putting it between two damp cloths ironing it and allowing it to dry flat. The end result isn't perfect and all the glue in the buckram fabric has disapeared, but I am hoping that it will be good enough to work with any way.
Currently I am sewing the wire to the cut buckram pieces.
And Rosy, thank you for the link. It had nog information about flattening the buckram, but I think it will be extremly useful for the rest of the hatmaking proces.