Help! I’m looking for a baby sling pattern (knit).
Found this crochet one: http://www.sleepingbaby.net/jan/Baby/crochet.html
Can’t find a knit one (yet) - did find a reference that a knit one might stretch too much and dig into your shoulder painfully.
I found a crochet one that was actually just a hobo bag. Knit ones would stretch way too much, but what if you found a knitted hobo bag that you think would work in the shape you want, make it in wool, then felt it? That seems like it would be more secure that way. You could block it in the shape that would fit the baby…I don’t know…
Or you could just make one of those fabric ones that look really simple: Easy Baby Sling.
I used a Baby Bjorn carrier for my baby and highly recommend them, though. It was really nice and worked well for a long time with my very heavy baby. 
Good luck!
I may have to sew one as I’m allergic to wool and any animal fur.