That depends how far you would go to define someone as “scientist.”
There’s no scientific qualification for being a scientist, so in that sense anyone who believes the world is flat could be called a scientist.
You might want to ask what the person’s qualifications are. For example, I’m an educated man. Been around the world a few times. Studied physics in college. I’m not a scientist, though. I’m a layman. So is the person a PhD? A doctor? Do they have a Bachelor of Science degree? Did they go to college even? Did they major in chemistry, physics, astronomy, astrology, astrophysics, orbitology, volcanology, geology, geometry, anything of that nature? Mathematics, statistics, theoretical physics? Do they have anything other than their claim they are a scientist to back up the claim?
I would guess there are not many, if any, real scientists that believe the Earth is flat.