There is not best way, there are different ways.
Export last frame as a frame, import and use that as a still.
Or cut last frame, set it to Hold Frame and extend/extract endpoint.
Or use Timeremapping: hold frame.
Or, if the source is still image (as opposed to a video clip), simply trim it out. To do so, select any of the trim tools (Selection tool, Ripple Edit tool, or Rolling Edit tool), click the end of the track item in the timeline, and drag to extend its duration.