Hi Booleano, that's a pretty difficult organic form. I guess I'd probably start by imagining the form before the fold which you could do with Loft through a set of curves like this:




Then the tricky part is you will need to manipulate the control points of the curves to form the folded over area:



Another method which could potentially be easier to control would be to make a folded shape on a flat plane and then apply it onto the Lofted base shape using Transform > Deform > Flow.

- Michael