Thanks! I could not find that, searching with my phone.

That post shows the method I was using about three years ago. In its essentials I still use this method, but the details have changed. The jig (or whatever you'd call it) that I use now is a long piece of 3/4" maple. Once the leather is clamped down to that, I hammer in a series of long thin wedges, also maple (or other hardwood). Each wedge has to be held in by a wood screw; otherwise it will shoot out again. Each wedge has to be a little shorter than the one that preceded it, so you can put the screw into the last wedge to hold the current one. Add more wedges until you can't add any more. You don't need to stretch the front of the saddle much, but the more you stretch the back, the better.

Here's an photo from September 2013 that shows something a little more like my current system, but the wedges are too short, so there's nothing holding them in; they can shoot across the yard without warning:


The white thing between the leather and the wedges is a piece of 3/4" PEX plumbing pipe. This makes it easier to pound in the wedges.

Once the leather is in the jig, all wedges in place, I leave it in for a pretty long time. Several hours minimum. When I take the leather off the jig, it's ready to be shaped into a saddle.