I sometimes refer to “side-stroke” as a lost art. In the past, it was an essential life-saving skill. However, many lifesaving courses now utilize a rescue tube as opposed to using a modified side-stroke to pull a victim to safety. Nonetheless, side-stroke is a useful survival stroke that is still taught in some circles.
The above video describes how to swim side-stroke. It covers the scissors kick, side-stroke arms, the full stroke, and side-stroke with an inverted kick.