Using a utility knife, cut through the inside layer of the paper connecting the lid to the box. Then, pull the lid off, carefully separating the patterned paper on the outside from the lid. (Skip to Step 4, if you're painting the outside of the box.)
Carefully remove the strip of paper that was holding the lid to the box, and set it aside for later.
Next, remove any paper or adhesive from the inside of your cigar box. If anything sticks to the box, use the sand paper to remove it all of the way.
Cover the decorative paper on the insides of the box with painters tape. If you're painting the outside of the box, you will apply the painters tape to around the bottom edges of the box instead.
Paint the box using the foam paint brush and chalkboard paint. (You will need multiple thin coats; I used 4 coats total.)
Carefully remove the painters tape (before the paint dries). Then, let the paint dry completely.
Apply a little craft glue to the strip of paper you save in Step 2 (spread a thin layer over the paper with your finger), then use it to cover the plain edge of the box. Hold the strip in place until it adheres to the box. (If you painted the bottom of the box, skip this step.)