We followed with the five shorter shelf nosings.
INSTALL THE BASEBOARD A 1x10 baseboard and base cap was installed last and helped
lock in the vertical panel on the back side. On the front side we toe-nailed finish nails into the subfloor to hold the panel in place until the finished wood floor locked it in place.
The top shelf is supported by a longer, wider cleat that is fastened to the wall studs.
Fasten the face-frames and nosing with combination of glue and finish nails.
The 1-1/2” vertical face-frames conceal the cleats, and the 1-1/2” shelf nosing conceals the plywood edge of the shelves. A baseboard installed at the bottom helps to stabilize the middle panel on the backside.
Once the flooring is installed, the tongue-and-groove boards lock the bottom of the shelf panels in place.