They are man made. Below is a documentary from Belgium where they investigate this topic after one poped up on a field. They manage to find a group of students making them. Watch from 20:30. They show the one they requested and then go about making it at night. It is a simple question of geometry using ropes as a giant compas (like the freemason symbol). Then they use planks of different lengths to trample the hay and create the paterns following the giant compas limitations.
It is in french but i will look if i can find the English translation.
https://youtu.be/dkt3AiD4yH0

Praise the all mighty Zesus. (Not a sun God)

Alone With Everybody (Bukowski)

the flesh covers the bone
and they put a mind
in there and
sometimes a soul,
and the women break
vases against the walls
and the men drink too
much
and nobody finds the
one
but keep
looking
crawling in and out
of beds.
flesh covers
the bone and the
flesh searches
for more than
flesh.

there's no chance
at all:
we are all trapped
by a singular
fate.

nobody ever finds
the one.

the city dumps fill
the junkyards fill
the madhouses fill
the hospitals fill
the graveyards fill

nothing else
fills.

There are other similar cults to freemasonry going on at the same time, we cannot pin everything on the masons though I would love to.
Masons also go by different names like order of the Eastern star, knights templar. Still the same cult.

look at some other ones..

What do you suppose they are up to?

Cgi Joe