With thread (wool, cotton, silk) or ribbon, the "berlingot" is easy and cheap to make.
You can make the size you want, just respect the ratio.
First score the lines with scissors (you can also use an empty ballpoint pen).
Glue tabs and let it dry.
Keep a regular tense (without crushing the cardboard !).
Threads don’t have to overlap (push with your nail if you had to).
Finished berlingot seen by top.