- flats you don't mind messing up. I recommend suede-finish kinds because it better matches the felt texture of the hearts. (you can find cheapies at GoJane)
- hot glue
- stiff felt
And here's what you do:
1. Cut out the shape you want from the stiff felt. My shape of choice were hearts, obviously.
2. Hot glue the shape to the flats. I only used one big dab of hot glue to anchor the entire heart and it hasn't proven a problem yet.
That it! See why this is more like a "guide" rather than an actual guide? Haha! I don't know how waterproof these are, but I have worn them in the rain a few times without incident. It shouldn't matter much anyway if they get ruined since it's essentially a $20 project, depending mainly on how expensive your flats were. Even if the hearts do get weather-damaged, you can always rip them off and glue new ones in their place.