Wow, Baxter, that is a beautiful bowl. You did a great job, and you shouldn't be worried about the flat spots. If you hadn't pointed them out they wouldn't have been noticed. And even now that they are more visible, they seem fine to me.
One other comment, not related to the bowl or signature, though. Clean your camera lens, man! Your breath and a microfiber cloth will go a long way to eliminating the dust spots in your photos.
It’s only work if somebody makes you do it.
A day can really slip by when you're deliberately avoiding what you're supposed to do.
Duct tape is like the force. It has a light side, a dark side and it binds the universe together.