The 'clapping' sound a Scrotum makes when slapped against
skin. As it would sound during excessive "male"
masturbation when the scrotum slaps against a palm, or during fast intercourse; when gravity and momentum
slap the scrotum against the partner's skin very close to an orifice. The area could be a chin, pubic region or anal region, depending on position of the two people involved.
Hooper knew what was going on in Bryan's bedroom because he could hear the 'Flot-Flot-Flot' from
outside the closed door.
Or,
As
Abel's scrotum 'Flotted' against her
skin, he was amazed at just how sloppy the sex was that night.
As a means of insult; Shut up, Flothead! Fuck off, Flot-Face! You've got Flot breath...