Your best bet will be to get a wrapper of the bar you chose, carefully open it and measure it. Let's say it is something like 8x6 or something (just a guess). Just start a new image in your graphics program, designating that size and a dpi of 300. Then design it and print it. If you have the option of printing crop marks, do that so you can cut it carefully. I don't think it will matter how you attach it - dbl sided tape sounds good but you could just as easily use a glue stick. If I were printing it, I would try to get glossy paper just because that's what the bar wrappers are on, but really any paper would be cute. HTH.

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