I made one but it didn't turn out the way I'd like. The points from each corner end up irregular since two sides are longer than the other two. The long 'points' (or flaps) are offset rather than centered. I modified it to be usable with a 'handle' added and a 2-button closure on the offset points/flaps. It was pretty fabric and was given as a gift to a friend. However, it didn't turn out as I'd hoped. Unfortunately, I didn't take a picture.
Adding double-wide/double-sided bias tape or binding after 'cutting down' the points to become horizontal edges would be a way to make a rectangular 'box'.