Start just downhill from the boulder that is typically used for Hagan's Wall. Choose from any one of several really bad edges and sidepulls to get off the ground and nab the pocket that you normally get with your right hand with your left. Use a small pocket just above with your right to get the big flake on Hagan's and finish with that route. A lower start is possible from the obvious, sharp, glued edge that will be at least V11.
This is similar to Christian Griffith's Yojimbo but uses different holds and sticks with Hagans to finish. Yojimbo seems no longer extant due to breakage.
The obvious but very hard direct start to Hagan's that begins just below the normal starting holds HAS NOT been done.
A less than obvious direct start that begins down and right from the normal start on innocuous and small holds (as described by Peter above) was done by Peter Beal in 2000. This one climbs up and slides left into Hagan's.
An even lower start to Peter's version that begins matched down at the glued crimp also HAS NOT been done.