Kurt Osiander, an old school Ralph Gracie black belt and BJJ cult hero, shows a really nice set up for the armbar from mount.
He starts off with a low mount, putting a lot of pressure and slowly climbing his arm to what looks like an arm triangle/Katagatame.
He then traps the head arm and sits back to then transitions to an armbar with 2 different set up options.
Try it out!
