Also I forgot to mention is to just add a drop of lube right where each spoke attaches to the rim, and make sure the rear wheel quick release is tight also.
I went for a long time and just knew it was my crank bottom bracket, but then found it was the spoke, so the sound can fool you and it can be in an area you would never suspect.
The fact that you say the creak comes at the 6 o'clock position of the crank tells me that it's due to some flexing at the end of your downward peddle stroke, and then as you shift your downward stroke to the opposite side you are getting a flex to the rear wheel which is causing the creak which sounds like what my problem was.