I wrapped a length of two-tone organza (from John Lewis) loosely round the crown - I didn't hem it, just cut it very wide and made sure that there were several layers of folding between the rough edges and the outside world, with the selvedge at the end and on top - then arranged the folds and stitched it all down, using a few beads to finish off
The peony was one I got from a Pound Shop - they often have lovely artificial flowers. I just pulled the stalk off and hot-glued the place where it had been to secure the petals, then glued it to the hat through the organza (which was more firmly stitched at this point.

I made this from a mould created from another hat: it was a good solid one I'd got from a charity shop, that I liked the shape of but didn't otherwise value, and I lined it with cling-film and then strips of artists' plaster-bandage.
When the plaster was dry, I took it out and smoothed it down a bit with sandpaper & DIY filler and painted it to seal the surface.

Then I used this to shape the sinamay. Not being very expert, and not having any technology, I did it in 3 parts - top of crown, sides of crown and brim - and used a combination of pva glue and stitching to secure them. I used 2 layers, and decided to make the brim wider than the original, just by letting the sinamay stick out over the edge of the mould along the bottom.
Then I turned the brim up and stitched bias binding round the edge - you have to do that by hand, because machining will stretch the edge out of shape.
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