Since I happen to like an optimized model I'd probably build the back in the Vertex Modeler: by creating circle, outside edges, the slat-like cut-outs, then (laboriously) hand-stitch all of these together with new lines. Once I'd filled the resulting surface I could then extrude and bevel. (Of course, not sure if Carrara5 will still let me do it that way. It seems it has decided all the obvious modeling methods are "incorrect" and must not be used any more.) Those legs might be possible by a series of cross-sections and a loft. If you plan them right you can get that change from square to round. Alternately, use the Dynamic Extrusion tool and stop in a few places to edit the cross-section by hand before continuing the extrude.