First I really like your drawings it looks so artistic and detailed.
Also, it’s a great idea that you thought about a healthy cookie that is a way from using flour it is rally interesting. I think your cookies name is so catchy and creative ;)

One thing, I wish if you thought about grinding the rice and then reuse it as a flour so you can shape it easily like how your plan was.

For the bowl cookie idea, what if you put a bunch of rice inside a cupcake pan and then place a smaller cup in the middle off it. So it looks like a cup in the middle of the pan surrounded with rice and bake it like that. I think if you used this technique you will get the result that you were looking for and have your bowl cookie !!