all the same size. just pin them on the felt and cut away.
hot glue (or use fabric glue) the ribbon in place on the inside of the back heart.
arrange and sew your buttons in place on the front of the top heart.
when i make things like this, i really like to hide all the knots. i like the polished finished look better. to do that with these hearts, start by hiding your knot inside the heart. sew down through the bottom heart near the edge, but inside a bit (as pictured above).
place your two layers of hearts together and go up through both layers of heart near the edge of 