There were/are many different ways to do freeform successfully.
Some DJ's could put a thematic set together like no other. Others could incorporate similar musical elements to educate. Still others could create musical canvases as backdrops to their appreciation of the day (Ed Bear particularly comes to mind). A very few could lend their dramatic talents to create stories...
My focus (1969-92) evolved into a keen interest to make my primarily music and primarily rock 'n roll program sound like one long song - seemless, one song flowing into another, with commercials and PSA's matching the flow.
My older son turned me on to modern dance/club/trance music about a decade ago. Talk about seemless mixing and the art of segue! My highpoint in appreciation of its freeform qualities came when "dad saved the rave" at Ward Valley, the summer of the Hale-Bopp Comet (1996?).
Here's a good Internet source:
? ClubFM Internet Dance Radio, Trance Radio, House Radio, Tampa Radio, Chicago Dance Radio, Las Vegas