I chose to trim the excess fabric from the first fold of the hem to reduce the bulk on the corners. Once again this is just a preference but I think it good habit in case the projects end up showing and this helps your corners lay flatter.
I did have to pin the hearts onto the edge of my runner before sewing and I'm glad that I did because my machine didn't exactly love the felt. It kept bunching up under the presserfoot, not sure what that was about.
Anywho, I used a medium sized zig-zag stitch to attach the hearts but you could stitch them by hand too.