Given 12/14/19 by Rabbi Mendel Kessin
Although this shiur (class) is part of a dedicated series, it covers material from the missing shiurim at the beginning of the Derech Hashem series.
The material not covered here is the Hakdama (introduction), in which the Ramchal summarizes his method of systematic learning & retention of material. Rabbi Kessin has dedicated videos of this method in videos and playlists on this channel.