Consider the EZ Face Mount Frame

For windows with no trim, only the dry wall surrounding the window, there is the EZ Face Frame. This frame sits on the drywall around the window and provides a trim for the window as well as a frame for the shutter.

The EZ Face Frame has a face strip which is removed to allow the frame to be screwed to the wall. After the shutter panels are installed, the face strip is replaced and the screw heads are covered, giving a completely finished look.