The phrase "a natural speaker" is correct and usable in written English.
It can be used to describe someone who speaks a language fluently and effortlessly, often implying that they have an innate ability or talent for it.
Example: "As a natural speaker of Spanish, Maria easily converses with locals during her travels."
Alternatives: "fluent speaker" or "native speaker".
Block is a natural speaker - likable, articulate, funny, confident, able to laugh at herself.
I was more or less a natural teacher, but I'm not a natural speaker.
There are dogs in Elsewhere, too, and Liz just happens to be a natural speaker of Canine.
She comes across as a natural speaker who establishes an instant rapport with the audience, and delivers her message in very simple language.
He is a natural speaker, who has the lilt of a preacher summoning his flock on a journey to the Promised Land.
From 1969 to 1973 she attended Radcliffe College in Cambridge, Massachusetts, and then Harvard University, where she obtained a degree in comparative government before, from 1973 to 1977, studying philosophy, politics and economics at Lady Margaret Hall, Oxford, where as a natural speaker, she was elected president of the Oxford Union.
He is not a natural English speaker.
He is a natural public speaker who built a liberal record in the House that could have served as the backbone of a bid for higher office.
My conclusion: I was not a natural public speaker, but I became a whole lot better than when I started.
Mr Kiir is not a natural public speaker either, but he knows how to work the crowds and is greeted with cheers and popular affection when he speaks at rallies.
A natural public speaker with an art for telling tales (thanks to a love of mythology and literature), she has taught marketing workshops and served as a storyteller in the Bay Area and at established venture capitalist and accelerator programs.
