Pattern Variations:

--I've tested this pattern using several medium (4) weight yarns and a 5mm (H-8 US) hook but theoretically you could use larger or smaller weight yarns instead by modifying the number of stitches in your rows (e.g. a smaller weight would increase the amount of stitches per row and a larger weight would decrease the number of stitches per row). The foundation chain length should be approximately the width of your phone plus 1-1.5 inches on each side to allow for stitching together. If you switch yarn weights, I suggest using the recommended hook for achieving a 4"x4" gauge on the label to keep similar ratios to the original pattern. 

--While I prefer to start with a foundation cord, using a foundation chain works just as well!

--If you want a ribbed texture for your pouch, crochet into the back loop only (BLO) of each stitch instead of looping under both. 

--To add some fun color contrast, feel free to use other weight yarns for the bag strap and seams!