The next part was to cut the sides of the case to 12” high. I set my handy dandy incra miter gauge to 12” and sliced off the bottom.
Since this is mdf with a thin veneer, I separated the mdf piece with the original dado for the bottom panel from the veneer and glued it back to the main side. Then I took my chisels and gent saw and continued the dado the way it was originally. Oh, I also added some filler pieces where the old shelf was.
Then I cut new mortises for the back support pieces:
Tada! Dry fit. Next I get to work on the face frame. Not sure how I’m going to handle to holes from the original hardware. More on the next episode of, “why’s this guy doing this???”