I apologize that there aren't pictures of the process. It's because I don't really have a long enough chain to make another one, but the directions are pretty straight forward and it requires minimum sewing.
If it really is confusing, I can probably add some pictures.
For styling, depending on what colors you use, and the length, I can see it going with anything, casual or dressy.
You'll want to find some sort of chain, it can be long so that the necklace hangs, or short if you don't want it flying all over the place.
After cutting out a template of a heart, (or any shape),on cardstock(mine was about 2.25" x 2"), cut the shape 2x out of the leather. Sew the two pieces together around the edge with the suede sides together.
The leather I used was relatively thin and flexible. Hopefully you don't break any needles like I did.
Button choosing-you want as big of a variety as possible, and remember, you're attaching them to both sides. I used some that were either brown/black/gold/gray etc. that were of various sizes because it went with my vintage theme, however you could use bright colors or whatever you want!
I figured out where I wanted to place each button.
To make sure no knots or anything showed up on either side, I decided to hot glue my buttons on (Also because my needles kept breaking.)
You may be thinking, what if I sewed the buttons on each half first and then sewed them together? My counterargument would be that when sewing on buttons, the leather might bunch up where the stitches are, and the halves might not match up. But if you think it would work, i'm not going to stop you.
This next step is really up to you. With having few resources, the task of attaching the pendant was unique. I took an earring with a loop on the head, and put the earring through the chain. I then threaded some thread through the loop and through the top of the heart.
If you had access to a real craft store, you might be able to find an actual thing to facet it with, but this is what I thought of.