This vest literally will take about 6 hours at most to knit up. Knit up in 1 piece with fake seams. 3-needle bind off shoulders and a few picked up sts around the neck and 4 rows of knitting and voila - you’re done. A zipper, frog fastener or big ole button is all you need.

It’s my version of the vests that all the kids are wearing.
Model shown in size 6.