Today I continued cutting T1-11 to fit the rough door opening. I realize that most of what I am doing is custom work and not necessarily standard construction! After I cut and fitted the first upper triangle of siding, I cut and installed the flashing. It will go over to the door frame, but can't interfere with the door sitting flush.
Here is a view of the flashing installed and the T1-11 cut to fit the rough opening of the door. I installed a scrap piece of siding to the right of the door opening, so I can position the door against the siding. I have to leave a space open that I can enter and exit through when I am installing the door. I checked and I can fit through there!
I did a test fit with the second triangular piece of siding and it fit nicely. I just have to trim the siding for the door's rough opening and then I can tack it in place. I'm getting close to being able to install the door. I need to buy some more caulking; the instructions for installing the door said to use an entire tube of caulking as a bed underneath the door.
All of this would have been much easier if I had put a layer of 1/2 " siding on initially, under the T1-11. But that is a story for another day.