Blurry picture, but this is what all the pieces should look like when they’re cut out.
We’re going to start with the ears.
Face the main and lining fabrics right sides together and sew with a 3/8″ seam.
Fold the ear together along the cut out V.
Pin them to each side of the hat roughly 2″ from, and facing, the brim.
Pin the rectangle to one side of the hat with the right sides together. And then to the other side of the hat.
Do the same thing, separately, with your lining pieces.
Once everything is sewn up, insert the main hat into the lining with the right sides together. This is also when you’ll insert the ties. I used ric-rac but any ribbon or string will do.
The bulk of the ties will be inside the hat with just an inch or so sticking out to get held in by the seam.
Sew around the perimeter leaving a hole to turn it right side out. You can then hand stitch the opening or just top stitch over the whole thing the machine. Top stitching would also help to hold the lining in better but I haven’t done it in these pictures.