This is quite a simple pattern, using only one type of basic stitch, and that is single crochet stitch. You will work this stitch alternating between inserting into the front loop and into the back loop, to get the desired texture of the bag.
This pattern is for the bag size of app. 10.2 x 13 in (26 cm x 33 cm), but with stitch number and row number modification you can change it into any size you like! It is very suitable not only as a tote bag but also as a laptop or iPad sleeve!