Cut out template from poster board with scissors.
Score along the dashed lines on all 4 sides of the tray (but don’t crease the folds yet).
Cover each side of the cut-out completely, with two contrasting colors of Duck Tape®. Allowing the excess tape to stick to itself around the edges of the poster board. Press the tape together firmly around the edges so you can see the outline of the poster board shape.
Trim away the excess Duck Tape with scissors.
Fold along the creases you made in Step 2, and use small triangular pieces of tape to secure the corners on the reverse.
And, you're finished!