I started with 10 wood shims. I left two the size they were, cut 4 about 1/2" smaller and the other 4 an inch smaller than they were. I cut them on the saw, but it is the thin end of the shim that is cut,so you probably could even use some scissors.
I added some paint to them, sanded them a bit, and then laid them out on a scrap board (this one is 16 x 11 1/2, but something a little bigger would probably be a little better). I did mark the middle of the board with white chalk to better place the heart.
I glued them down with wood glue.
I used a board and some weights on top while the glue dried.
A little polyacryclic on top for some shine and that is all.
Simple and sweet.
See some past Valentine's Day ideas HERE