Share 'fixing a snapped fiddle neck'

I have a violin without a fingerboard.  The neck is broken clean in half right below the head. I can get the two pieces to nest back together and glue them, but I also want to add a splint on the fingerboard side of the neck.  How do I cut the slot for the spint to go into?  It won't be much longer than 1" or so, and maybe 1/4" wide.  Discuss!