I am looking for F/m or f/m told from the 3rd person or the spankers PoV where the m is a teen

Storys where a teen boy is spanked by one or more females adult or teens. Where the girls seem to get at least some enjoyment out of it.

I think there is one called rear window that starts with a boy getting trapped looking out a window and a group of girls take advantage of it and spank him for the fun of it.

or authors who have written such stories?

I suggest using the very good search feature. Of my own stories, perhaps you’ll like Hamm on rye and it’s sequel and 8 rules for dating my teenage daughter.

Crimson kid has dozens of such stories. The search is the last choice of the submissions menu.

I have several of those stories.

Go to the "Submissions" drop down menu. The last item on it is "search". You can set the terms for:
Age(s): Teen, Adult
Spanker: F
Spankee: M
Pick what kind of instrument (or any) you like, hit search, and you'll have a long, long list of stories to explore.

That search feature is only there for subscribers.

As a regular member you can go to Info -> Author's list, where you can select the preferred age category and orientation. Then click Filter and you get a list of authors who have written stories in those categories. You'll have to go to the authors' pages and look up stories there. A bit more work than using the search feature, but manageable.

Some stories you might enjoy (although the m is an older teen/young adult), written from 3rd person:

Lost in Translation by Lurking Col. A 19 year old guy goes to study in South-Korea for a year. The 18-year old daughter in the family where he's staying tricks him into getting spanked by her mother while she watches and enjoys herself.

The Peeping Tom's Comeuppance by BashfulBob. An 18-year-old spies on a classmate getting spanked by her father, and ends up getting spanked himself by two female neighbours.

Oh, I didn't know that the search worked like that.

Go to my author page at https://www.thespankinglibrary.org/index.php?func=authpage&author=Goodgulf

Look at the story codes. You will find many F/m stories. I'm not sure about all the witnesses, but there are many Pink / blue coded stories that are a/t or t/t

Hello Frosty, I think that some of my stories especially most of the latest ones will meet the criteria. Check out my author page and let me know if you liked what I've written.

I think my "Schoolboy" ticks all of your boxes.

Geoffrey Stirling

Yes, that is indeed pretty much 'right up my alley.'

I haven't been writing much lately due to personal and medical issues, however offhand I can recommend these works of mine in which teenage boys are spanked by women and/or girls:

"Here's to Good Luck!" serial (It combines two of my favorite situations, cheerleaders spanking a male athlete and a boy paddled inside a girls' locker room.)

"Island Excursion" (kind of a sequel to the serial)

"Agreed" (two girls spanking the male cousin of one of them)

"Champagne and Paddywhacks" (long story with lots of spanking by females, of both boys and girls)

"A Promise is a Promise"
"A Promise Extended" by Tyrport
"Babysitting Fun, Spanking Style" Part #1

(I still hope to continue this account, but for now it's a story trilogy, Tyr's part was written with my approval.)

"Eavesdropping, Peeping and Asking Nicely"
"Incorrigible"
"Paybacks and Payoffs"

(This trilogy involves mostly the same characters as the other one, set a touch later in time.)

"It's Not Fair!" #s 1-5 (letters from spanked-by-females boys to a magazine)

"It Sure Is Fun!" #s 1-4 (letters from girls about spanking a boy and/or witnessing one being spanked by females)

That should be plenty for now, perhaps I could indicate more later... --C.K.