Thanks for sharing this, it’s awesome. I tried doing exactly this with storage spaces, but i couldn’t chose just the free space so I gave up. Now with your solution, it works!
I was refered to your post via my own enquiry to achieve the same kind of result in a different way - and without raid. I would love to be able to automate your process in powershell.
Do you know if there’s a way to achieve the same result in linux with LVM?