Plus, you'll gain respect on the playground this year after your mom springs the extra $4 for a laser background....
Step 1: Print background
Simply print out these 12 images and lay them out to find where they go. Be sure to print each 100% to scale (see my screenshot for reference), without letting your printer re-size to fit the page. Chop and glue each piece to each other first. Then, once satisfied with your paper sheet, carefully use spray adhesive to attach to your backing.
**note: there's a little bit of overlap with these images, but not much. Be sure to work meticulously so your pieces all line up.