I set up a free board at
I inserted Mori's Code Wrapper gadget in the page: Insert, More gadgets, search for Code Wrapper.
(Mori's Code Wrapper gadget may no longer be available but the Embed Gadget also works.)
I set it to 100% wide and 1200 pixels high and inserted the code generated on the groupboard site.

On a sub page I inserted the admin code they sent to me in an email after I registered.

Code Wrapper

Embed gadget

Subpages (1): Groupboard Admin