You're going to need a woven wrap mama to do a back carry. Despite the instructions on Moby that show you can do a back carry, it's really not safe to do it. I really wish they'd just take that out of their site and their manual. There's too much stretch to do a back carry safely and securely enough, especially when you are just starting out.
For baby back carries with a woven wrap, check out this link for a
back wrap cross carry. You can also find videos of this carry on youtube.com and also look for one called secured high back carry.
Practice over something soft and with someone behind you. Take your time and practice every day. It's worth learning for sure.