I found 2 very damaged straw hats in an op shop for very little a few years ago. They had a circular high crown with a circumference too small for my head.
I needed to make it larger, flat on top and oval. I pulled out all the thread and soaked the straw in hot water.
Once wet I pinned the straw with long quilting pins. I then sewed the straw into shape. When wet the straw is very flexible. It will even dry warped if you leave the pins in. Thankfully another soaking will help smooth it out.
Once it was sewn I steamed it smooth and into the desired shape.
My hats get a lot of use and from experience I've learnt to always reinforce my straw shapes. I tacked milinary wire to the inside of the brim.
Next is my favorite part.. trimming. I reused ribbon from a bonnet with too long ties. It was too short, so I left a gap in the front. I tacked the ribbon and added extra gold ribbon from my scrap stash.
Next I placed flowers from my milinary box. Most were birthday gifts from my husband when I was pregnant. I twist and pin the flowers until I have a design I like.
The reason it does not need to be neat is because I will line the brim with silk. I cut a strip of silk the width of the brim with seam allowance included.
I then ran a single father stitch and tacked it just inside the edge of the brim.
Once fully attached you can pleat or gather the silk into the crown. I like to pleat and I'm not over careful as the brim is curved which changes the way it appears anyway. I tack the silk down with a curved needle.
From here I have 3 options depending on how OCD I feel about a part of the hat no one will ever see. I can full bag line it on cotton, I can trim and bias tape the silk edge or just whip stitch the silk ends in place.
As the silk is shedding bad I decided to bias tape the edge as leaving the top unlined will hopefully help with air flow when it is very hot.