I don't know about mochila. Guess I will have to do some searching on that one. I have been making soap sacks. (Supporting A Community with Kindness). I've made 15 so far and still have plenty of cotton yarn to go. I'm not sure which organization I'm going to give them to (Red Cross is easy to locate, but I think I would like to give to homeless vets the first time), but I'm sure there are plenty of groups that could use these.

and, one more thing
You always only work in the back side of the loop.
The front, unworked part of the stitch gives it part of its distinct style/design.