Outer frame under construction
Here you see an end assembly on the bench, with top and bottom aprons for the backside sticking up. The front apron with drawer cutouts is visible on the bench, and the other end assembly is on the floor. It  is critical that the back of the aprons are in the same plane as the surface of the notch in the columns. This will allow, in subsequent steps, for the face frame, side panels and back boards to seat cleanly against the columns without visible gaps.

Finishing up the Outer Frame
The tenon of the front upper apron is inserted into the top column mortise. I glue and clamp the frame, waiting to install the pegs, all at once, when the whole case is assembled.

Inner Frame panels going in
In this photo you can see the completed outer frame - eight aprons and four columns. I have clamped the inner face frame (defining the door and drawer openings) as well as the back panels into place and am checking their fit.

Face frame, side panels, back panel and floor installed
You can see the dado in the back to accept the partition between the graduated drawer bank and the under-sink area. The floor went in last, fastened to cleats from underneath.

Fitting doors and drawers
The red inside the drawer cavity is lumber crayon. It will transfer over to the drawer parts where more trimming is needed for proper clearance. You can also see that the false drawer front near the sink has been installed.