8.5 x 11
Cut at 4.25" down the long side to make 2 pieces each 4.25" x 11"
Score along the long edge at: 0.5" 1.75" 5.75" 7"
Score along the short edge at: 2.75"
If you're a more visual person, here are some pics
Once the box card is assembled, take one scrap and cut it 1/2" wide, scoring the edges to make it fit across the center of the box. You will attach your images to the center-strip. Here's a pic of what I mean.
Leave me a comment if any of the above is unclear.