I love unfinished wood because the potential is endless, however, I'm not a big fan of painting them first. A great, but messy, alternative is using Tim Holtz distress stains in a color that coordinates with your paper. Fortunately I had a color that worked on hand and was able to stain the box first and then cover with paper.
For the sides I cut a 12" long strip slightly smaller than the width of the side. I then cut them in half and met them in the middle. I did this with this paper so it wouldn't end up upside down on one side.
The envelope and "LOVE LETTERS" are stickers, attached with pop up adhesive, and the LOVE forever yours portion is fussy cut from a scrap piece that I was able to salvage a portion of.
The hearts are all fussy cut from one of the sheets of patterned paper and I distressed with a little red ink and adhered them alternating between glue dots and pop up adhesive.
Thanks for looking ~ Michelle