Constructing irregular polygons is possible using CSG operations, or even by computing the absolute positions of the vertices of the boundary. An alternative is to use relative 'turtle graphics' commands to walk the boundary and then convert these steps to a polygon and hence to a 3D object The examples are designs for a cable tidy. The first is a simple one polygon design. The second uses two joined polygons for a better design. It also uses a simplified turtle language which is quicker to write. Code uses let() and concat() so isn't yet compatible with the customiser. The approach is generalised for any 2D shape. see my blog http://kitwallace.tumblr.com/post/114490020854/irregular-shapes-via-turtle-graphics