I now had to address the extra wide dado that from the miscut. Using the bandsaw, I cut a piece of scrap to length and width that fit pefectly in the gap. Then glued the shelf, extra piece, and the back all at once, which completed the glue-up.
This is what happens when you don't pay attention!
The top photo shows the filled dado. I had to try and make the best of an ugly sitiuation. It just so happened that small corner was the perfect size for my block plane. I cut another small piece of scrap and glued it in between the shelf and the bottom.
I got lucky with this mistake as it happened to be the perfect size for my Block Plane.
Everthing was sanded to 220.