Slotting plywood together

Hi all - relatively new to woodworking and don't have a huge amount of tools or experience etc.

I have the idea to make a shoe rack from the cheapest thing I could find locally (9mm plywood). I would have liked thicker, but price was putting me off.

I am planning to just slot the plywood together. But haven't had any experience of doing that and cant find much at all on the forum or internet - maybe becasue it's so simple , no one bothers to write it up?

Do I literally cut the slots at 9mm? I don't have a router or table saw , so would I just see what my circular saw blade removes and work around that?
I plan on 3 'legs' / cross section pieces and 3 shelves, so would it stand and support itself or do I need to do something else ?

Any tips appreciated.