This cardigan is constructed from at least five different crochet patterns/motifs, a large portion of which were pieced together with the trellis stitch. The sleeves are based on a scarf pattern, which is also used in the upper body of the cardigan.
The cardigan's buttons are also crocheted.
Following is a rough description how I put this cardigan together. I also used a simple schematic for a summer cardigan such as this below.
You may use any cardigan schematic to determine the shape and size of your cardigan - and feel free to modify.