Note that the preview window is not wysiwyg unless yor click on 1:1 Corner View. Only the width is correct in both views.
Use this filter only on layers. If you use it on the background Layer, the Frame will be solid black.
It works by making the frame area transparent, which allows the underlying image to show through.
The underlying image becomes the frame. Apply any effect you like to the lower image.
The example below shows that the Middle layer has been toned sepia and brightened to frame the color photo.
The lower layer, which will become the frame, doesn't even have to be the same image as the upper layer.
The possibilities for frame design are infinite!