The hearts are made of the same fabrics that my Heart Quilt is made. I had a lot of fabric leftover and never throw any usable fabric away.
They were lined with lightweight batting so they are puffy, then backed with muslin that had a large buttonhole sewn into it to turn the heart after sewing. They are attached with stick on Velcro circles. The Velcro may need to be sewn on eventually because it doesn't stick forever. To make it more efficient I turned the Velcro over on every other heart. That way when I need to put shamrocks on I won't waste 8-9 pieces of Velcro to use just one side on them. Does that make sense? I can turn the Velcro over on every other new attachment and place anything I want on the original burlap without wasting Velcro buttons. Frugal--it's in my blood.
Happy Valentine's Day