You can stuff with a prefold. I actually trimmed half of my econobum prefolds so that they fit perfectly on the medium setting for my flips. So you could always trim them if they are too long to use as the insert. The first site uses T-shirt material as their soakers - 2 soakers each of 4 layers.
Good luck! I would love to see/hear about your results!
I had thought about this too. There are a lot of patterns online esp. Etsy. My only real contribution is that I would sew the prefold to the front and only the middle part for that it unfolds still
You could probably convert a cover to a pocket pretty easily if your crafty. I would be afraid I would ruin the pul by sewing it through. It might be easier to convert your prefolds into stay dry inserts that you could just lay into the covers. That's should be pretty easy for everyone. Basically you could just trim or fold and sew the prefolds into the right size to fit into the covers. Once dd got moving I mainly trifolded.
Re: Using Prefolds to make AIOs
I am also looking at making some pockets. Here are the sites I am most interested in:
https://fernandfaerie.com/sewing_fitteds.html
https://www.modernalternativemama.com/blog/2009/11/29/cloth-diaper-tutorial.html#.UCrYMe1wpSV
You can stuff with a prefold. I actually trimmed half of my econobum prefolds so that they fit perfectly on the medium setting for my flips. So you could always trim them if they are too long to use as the insert. The first site uses T-shirt material as their soakers - 2 soakers each of 4 layers.
Good luck! I would love to see/hear about your results!