I've been working on the frame and panel for the back of the cabinet. This frame is composed of the same wood, European beech, as the cabinet. The components of the frame and panel back are two outside stiles, a center stile, and the upper and lower rails which are continuous along their length. The width of the individual components is approximately 2 inches or thereabouts, and I based this on aesthetics along with availability of clear quarter-sawn beech stock on hand.
The type of joinery I have selected for this back is the mortise and tenon. The stiles are of equal length, so are the the respective tenons at either end of each stile, which also fit into the grooves in either horizontal rail. In the photo, the frame is temporarily installed in the cabinet back recess for a test fit. I am in the process of creating the panels to fit into each of the frame halves.
Some judicious planing is involved in creating a perfect fit of the frame and panel into the back of the cabinet, but I had already allowed for this with a very small fraction of an inch in extra width of the frame. Another factor in the decision for the stile and rail widths is the factoring in of any small wood movement of the rails and stiles in their widths. The wood I have selected is fairly quarter-sawn so movement is substantially reduced and the fairly narrow widths of the components reduces the remaining movement considerably.
The panels will be floating with a small gap around each edge to allow for wood movement. Once I have this frame and panel back installed, the cabinet will have developed an entirely new look, that of a cabinet without front doors.