Instead of having all of the files under /board/ you would move everything to /.
Once there, that will have all the pages, databases, etc all show up correctly. By default, forums would change to /forums/ path instead of /board/. It's easy to edit that however. If you want it to be /board/, from the AdminCP, just search for "Customize Friendly URLs". Search for any mentions of forums/ and change it to board/. (There are 2-3, so it's a simple quick edit.)