I have a core box bit and I would like to add a trench if you will around the cutting board abot 3/4" in. I do not think you can do it with a router table and i know it has to be done with the hand router. How should I do it? The best I could think of was having a frame around it but there bit would be much to far in, and if I did make it bigger then I only risk the cutting board going flying in some direction and hitting the frame. I could just do it and then cut the wood but I do not want to waste the wood like that. What is the best way to do this?
If you don't already have one, get a 'router guide bushing' that suits your router. (You might have to replace the base plate to find a bushing that fits.) The only sizing requirement is that the interior of the bushing is bigger than your core bit.
You'll want a rectangular chunk of something to sit in the middle of the cutting board. Size it to give you the cutting path you want. (It can be any material -- it just needs smooth edges.) Hot glue or double-sided tape the guide to the cutting board.
Take progressively deeper cuts -- just a little at a time. The only hard part will be turning around the corners cleanly. Hold on tight and it'll go fine. If you nipped a 45 degree off the corners, it'd be a touch easier.