I made this summer lace granny square vest a long time back, something like 10 years ago which is why I don’t have a pattern to share but I believe it isn’t really that difficult to duplicate. As you can see from the picture below, it’s basically a lace granny square pattern and I joined the squares as I went along attaching them together always on the last round.
One thing to note is that I modified the squares to shape the armholes and neckline. Yes, I know. I wish I was more of a write-down-the-pattern sort of person. But somehow I work best this way, just shaping things as I go along. Maybe I have this fundamental belief that nothing is ever too difficult and I bet anyone who knows how to crochet would sooner or later figure this pattern out!
The other thing to note is that this vest is made in an entire piece with no joining seams at the side or shoulders. It’s really one piece.
Finally I attached to the back neckline a separate piece of ‘lace’ which I made out of several flowers joined together still using the same yarn. This gave it a bit more shape for the back neckline and the vest did not fall open or fall off my shoulders as it tended to do before I added the ‘lace’.