Here's where I got my inspiration. It's not exact, but close enough for me!
Here are the pieces you'll need:
Start by lining up the points and adjusting the top material to fit the shape, like so.
Then make some mirrored pleats.
I swear by Fabri-Tac, it keeps everything in place. If you don't have it, pins work great, too.Pin and sew.
Cut off the excess.
Pin those babies together!
When sewing, start near the point and move up, and once you've come full circle, make sure you've left room at the bottom to turn it right-side-out. (You'll see what I mean 4 pictures down).
There will be a little bit of excess Tshirt material around the scoop of the neck, to ensure you sew the two pieces together properly, just trim it.
Well lookie there!
Start sewing at the point and make your round again, with a 1/8-1/4" seam allowance. (Below shows where I started my back stitch).
And there's a nice little opening at the bottom for me to pull it's guts out. Do just that.
Once it's right-side-out, iron the seams flat, and fold the points under to make a "finished" edge.
And voila!!!! You're done!
I still need to add the snaps (or Velcro if you prefer) but that's very easy, and they come with instructions when you buy them.