Note: the width of the envelope will depend on the size of chair you're using, but my measurement was 18" wide. Once folded the length of my envelope was 13" tall. Finally, the flap that goes over the back of the chair drops down about 9 1/2" (again, this will depend on how tall your chairs are). Unfolded, my poster board was approx. 36" long and 18" wide. (Yikes! This is sounding confusing! I hope this makes sense!)
Once folded, I took some poster board scraps and make a faux envelope flap. Then I used a red sharpie to make it appear like it's stitched. I glued that to the front of the envelope, at the top where it opens, but I did not cover the opening. I completed the look with a red heart on the front.
Finally, I punched holes about 1 inch apart on each side of the envelope. The final step, stitching the sides with yarn, will be done by the kiddos next week.Below, you see how it sits on the chair when you're all done. The top of the envelope is open so things can be dropped right in.
Hope this inspires some craftiness! :)