As you can see from the photo above, the stitch used to attach the letters is a simple running stitch and the stitch to attach the front and back hearts together is a blanket stitch.
They are double sided. One side has the heart within a heart pattern and the other side has the letters. I threaded them together with a thin ribbon. What I like about them is that when they are hung from the ceiling or doorway, each heart would gently twirl like a mobile.
An optional extra is that sometimes I would add fragrance oil to a cotton ball and put it inside with the stuffing. It then becomes a scented heart mobile!
I've also made plain ones as well. The options are endless...you could use different colour combinations and different stitches too.