I did a similar one! I made mine square at the base and flared out to be circular at the top. Was a fun project. I will look and see if I can find a picture.
Edit:
Had that backwards. Circular at the bottom, square at the top. Found a pic but it won't upload.
Nice work! You should look into a dog leg gouge I think they are called. They make it so easy to get it and remove material specifically get the inside walls concave for the traditional kuksa look. I remember making hiking miles with my axe because I didn't have any birches near where I was camping haha. But yeah awesome work!