After it has been traced with chalk, pin the middle to keep both sides together
Cut out your hearts. Keep the pins in. Set pinned hearts aside.
Do the same with the other rainbow colors.
Now sew both pieces together along the edge in a extra wide stitch with contrasting thread. You could also handstitch these. Leave 2 inches open to add the batting.
Stuff the batting into the heart and sew up the last inch.
Do the same with the other colors (I only ended up making one of each color as opposed to the two I had cut out).
Thread some bakers twine into a embroidery needle and poke through the top end of one, threading it through to the other side. Make sure to put the hearts on in rainbow order.
Keep adding to the thread until they're all on.
Tada! Hang in a doorway or window!