Example 1: Square Facebook thumbnail photo. In this case, the original 16:9 shot is zoomed in and cropped.
Example 2 : A moment from a square video with subtitles. The original 16:9 frame is slightly zoomed in and cropped. The video's title is placed in the upper part of the frame and the subtitles in the lower part.
In this example, the frame is white, but the color of the frame may vary depending on your logo and other elements of the set.