In a writing group, we were challenged to write a cento in a given time from poems we were handed. A fun exercise!
Many years ago, in a writing class, I’d taken all the student poems which had a line or two rejected or criticized for whatever reason and placed them together in a poem. I read this in the same class and our Professor recognized what I’d done and appreciated it.
“UnWalden Pond” was published in That’s Going to Hurt a few years ago.
Centos are fun poems to write. Some publishers require citations for each line. Some publishers do not. I think it’s probably a good idea to keep notes of where you got what and call a cento a collage, patchwork, or otherwise identify it for what it is.