If you are looking for a simple and quick vest, try this.

The Front and Back are crocheted together in contrasting colors and continue to slip stitch around the armhole.

Method used:

Alternating cable CO and BO
https://youtu.be/pu20U6PdlXg

3-needle BO method:
https://youtu.be/EgV02_lLyec

How to crochet Front & Back together:
https://youtu.be/xas7SnAOArc