This pattern is a great way to use leftover yarn or mini skeins. It works with any weight of yarn; just use an appropriate needle size that will produce a tight fabric. The bag in the photos uses 8 colors of fingering weight yarn for the bag and one color for the I-cord. Total yarn weight was 60 grams, 40 grams of assorted colors for the front and back panels and 20 grams of a coordinating color for the I-cord join, strap, and button loop (optional).

For larger or smaller squares, simply increase or decrease the number of stitches you cast on, always casting on an odd number.
You may also adjust the size of the bag by using more or fewer squares; the basic schematic stays the same.