Very interesting. So we can derive the phonetics from those provided for coq au vin (/ˌkɒk oʊ ˈvæ̃/), which I have apparently been mispronouncing for a while.
The o sound is slightly different. More like the first o in bottom
That sounds the same to my ear. At least the way I pronounce both words. c-awe-ck and b-awe-ttom.
I believe in most North American dialects "corn" is one of the only open "o" in common usage. Try to pronounce an "o" without ending it in a "w" sound. Just holding it longer... and then stop without closing your lips.