This pattern uses the Mosaic Inlay stitch, which uses single crochet that are made into the back loop of previous row and double crochet that are made into the front loop of the 2nd row down, There is also the Border Stitch which is a normal sc through both loops at the beginning and end of each row.
I used a size 4 crochet hook and some double knit wool and the size came out at approximately 34cm x 42cm, you could experiment with different hook size and different thickness of wool for different sizes,
I intend to make quite a few different designs that will all be the same size so could be used to make a blanket, bag or anything else you can think of.