A CPL who is not an instructor could do remunerated trial flights under an AtoA AOC, but the "student" couldn't log it, they'd be a pax. This is the rule used for things like tourist Tiger Moth or Dragon Rapide flights at various places.
Otherwise you need to be an FI, as various others have said.
I'm sure as a CRI I could do much more flying if I could do trial lessons, but I can't.
Nothing to stop you taking friends flying for free of course. We all do that, but it's just a private flight with a pax.
G