I'm working on a very simple beamer theme for my presentations based on the default beamer template. I would like to make it a bit like a transparent handout with the white background and a bold rounded box (of the constant size) around the text contained within the frame (which would define the margins for the inner text and have some distance from the page borders).
I understand I should put this probably into the background or background canvas template but I'm quite stuck on how to actually define that frame (using which package for example).
Could somebody point me to such a package or give a tip for the solution? Thanks in advance.
P.S.: I would like to avoid creating an external image file and including it on each page.