Are you a "naked" button hole girl or a "fill the holes" fan? I can do both, but I really do love the look of a button with its holes threaded with something!
Here are my favorite ideas to fill/thread those button holes and a few tips!* thread with twine, sewing thread, Baker's Twine, embroidery floss, or super thin ribbon. You don't have to knot this material on the back, either. I have found it makes my layouts bulkier than they need to be. Just use a glue dot to keep it down. As a bonus, the glue dot will adhere the button to your project.
* no matching floss or twine? Cut super thin strips of paper that match your project and thread this through the holes. Again, just use a glue dot to keep it in place on the back. The fun part of this idea is the paper can be cardstock or patterned paper!
* threads from or thin pieces of fabric can also be threaded through buttons.
* use a Slick Writer or Sharpie to draw "stitches" on your buttons so they look threaded (this is the ultimate lazy scrapper technique

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* if you don't want to thread the material through your button, you can just tie it in a small bow or knot and just glue dot it to the center of your button. This is another great lazy scrapper technique!
Do you have any more ideas to share cover up those naked button holes? What are your favorite ways to fill those holes?