While reading The Things They Carried I came upon this scene:
Is this something that actually existed? Was it a satire poster, or an actual product? A blow-up doll? A target for target practice? 
Prior to the VietNam war, the word “gook” did not have the derogatory connotation it does now. When I was a kid, gook was similar to gunk or glop or other similar words.
*The Things They Carried * is ABOUT the Vietnam War.
[Emily Litella]Never mind.[/Emily Litella]
In the short story? The poster’s a joke the Green Berets made. In the tent, there’s a “pile of bones, all kinds”…trophies that the Green Berets took, and then next to them, a poster that says, “Assemble your own gook! Free sample kit! [the pile of bones]”
In other words, there are enough Vietnamese bones there that you can make your own.
I think you misread the story. There are bones and such inside the tent, making the poster a macabre joke. It’s not a real thing.
ETA: what CA said; what an odd coincidence of timing.
When I read the thread title, I assumed it was about making your own soup*. You know, like restaurants where you design your own sandwich or stir-fry or hot-pot.
*The first I was exposed to the word “gook” (국) was in the context of Korean soup. I didn’t even realize it was an American slang word also until recently.
Ha, I had the same thought as Pleonast. That’s a pretty creepy sign, I have to say.
I remember someone (a celebrity I think) telling a story that someone he knew used to make ‘assemble your own rat’ kits, or something close, and send them to friends. The kit included all the rat parts; legs, tail, head, and organs, along with ‘instructions’ (with photos!) showing how to assemble it. I haven’t been able to find a reference to this online, but I think I am remembering it correctly.
I don’t think anyone I know has a sufficiantly morbid sense of humor to appreciate that type of joke.
That’s what I thought, but the possibility crossed my mind that O’Brien was referring to some kind of joke item or propaganda that actually existed in those days.
FatBaldGuy, the term gook predates the Vietnam War and actually is thought to originate during the American occupation of the Philippines, specifically to prostitutes. 
I suppose it may not have entered everyday usage until Vietnam though.
Ah, the joys of teaching a Wartime Lit class.
Pleonast, I know how to assemble my own 국. 
I’m pretty sure that the word “gook” comes from the Korean language. “Han/Gook/Mal” means “Korea/country/language.” I think during the Korean war is when GIs started using “gook” to mean “asian person”. I don’t know if “gook” was a pejorative during the Korean War, but it sure was during the Viet Nam War. If any Korean speakers want to weigh in here, I would be pleased to have my ignorance fought.
The theory is that the American soldiers heard the Koreans saying “mee-gook” (Korean for the US, also a slang term for American soldiers) and thought they were calling themselves gooks.
But as I previously mentioned, the term gook existed from the time of the American occupation of the Philippines, which was the end of the 19th century, so it couldn’t have originated in Korea.
It looks like, in the early days, the term didn’t just refer to East Asians, either. From “The Conquest of Haiti”, by Herbert Seligman, published in The Nation, July 10, 1920: