you can make the lip out of quarter round trim molding.

http://www.imperialdesign.on.ca/ELEM...NDS/rounds.htm

and then 45 degree the corners and make basically a picture frame so the flat sides face the inside wall and the top, with the round portion on the inside. That should allow enough wood to get some small nails in to secure it to the top.


However, I'm only an idea man. I couldn't actually put this together if I had too.