It isn't but you could plain a rock and draw a circle on it and remove the stone outside the circle so it becomes a wheel
Also there is no such thing as prehistory that's an obsolete concept from the 19th century
it's much more complicated to work in stone than wood. stone cleaves horribly and the first wheels wouldn't have been made of flint.
a wheel isn't just a circle that can roll. a log isn't a wheel.
how to make a wheel:
find cylindrical tree at the top of a tall hill
roll it down
repeat until it's round
chop it into slices
put a stick through the middle