This Mochila is made with single crochet through the back loop. You crochet over 6 yarns. This will make the bag very firm.
This pattern is for the more experienced Mochila makers.
A Mochila is made with mercerized cotton, 125 meter / 137 yards per 50 gram.

The pattern has 21 pages and includes: 
Written instructions for the Mochila technique.
Links to videos to explain the technique.
Written instructions for the oval bottom.
Graph for the oval bottom. With the increases marked.
For the side pattern there is only a graph.
Pattern for a crocheted strap.
Pattern for a plain weave strap.
Pattern for a supplementary weft strap.
Instructions how to attach the strap to the bag.

The bottom is about 29 cm / 11.4 inch by 10 cm / 3.9 inch. and the height of the bag will be about 22 cm / 8.6 inch. The size can vary, because everybody crochets differently. If you use different yarn, measurements can be different.

Materials used: (based on 50 gram skeins)
2 skeins petrol
1 skeins gold
2 skeins strawberry
2 skeins aqua
2 skeins dahlia
Crochet hook 2 - 2,5 mm
Magnetic closure