I had all intentions of showing in full detail how this slot was cut into the bottom of the post.
I took step by step photos of the Timber Framer with his home made jig he used to hold his chain saw flat and level to make this slot. It was an impressive jig.
But I had problems with my camera right after the above photos.
Here is a shot of the chain saw and jig:

But as you can see the camera was a bit fuzzy!
I changed batteries and checked all the settings and everything was fine, but I couldn't get it to work at all the rest of the day, yesterday. Today it works fine. Why, I don't know?
It could be one of those things, "we may never know".
I wouldn't waste any more of our time posting blurry pictures but I hope to get a set from a local newspaper photographer who promised he'd send out some of the ones he took.
I'll be traveling back up to the site tomorrow, with this camera and a spare, to pick up a timber framer friend still there and I hope to get some more shots of the completed frame.
If my camera(s) are still working correctly and the timber framer with the chain saw jig is still there, I'll ask him if I can get another set of photos of the jig. He invented it, and doesn't intend to patent it. I told him I intended to post these photos of his jig on this site, and post his name, business name and location, and he said it would be alright with him, if I did (I wanted to give him credit for his invention).
I could draw it some time, but why bother if I can get a photo of a working model.
DanG, what more info were you looking for?
Jim