RECTANGULAR FIGURE - bust, waist and hips equally wide

Distract the attention from your waistline to either neck and shoulder (top) or skirt and trousers hem (bottom).
 
Outfits cut on bias help at giving you a shape. Just be aware that a soft cut on bias fabric can reveal too much than necessary.
 
Lowish neckline and low waistline helps to redirect the eye from the waist.
 
Use fabrics with vertical lines when possible, gore skirts and dresses with flare hemlines.
 
Avoid prints that are all over your outfit, like tartans, horizontal lines or big spots. Three quarters and elbow sleeves are very unflattering.
 
1920s French Fashion will suit you perfectly! Everything is low waistline, concentrating on hips, necklines and hems.

FEW OUTFITS SUGGESTIONS FOR A FLATTERING RECTANGULAR FIGURE:

Dresses - Princess , A-line , Low Waist Ball Gown
 
Neckline - Long V-neck , Square, Bauteau , Wide Scoop , Wide Scalloped
 
Skirts - Pleated Border, The Gore Range , Low Waistline Yoke
 
Sleeves - Dolman , Kimono , Bishop (the short sleeve) , Long Bell, Magyar