The author made the speaker out of foam plate as the best quality of sound is produced by the materials that are lightweight but are strong enough to aviod excessive vibration. Paper plates are too soft and plastic disposable plates produce excessive vibration. So foam plates are best.
First, roll one strip of paper over the magnet. Use tape. Do not tape the paper to the magnet.
Roll the second paper strip over the first one. Do not tape the paper with the first roll..
Glue the paper cylinder to the plate; try to glue it exactly at the center of the plate..
Start making the coil, keep the magnet inside so you don't crush the paper cylinder..
Fold the business cards as the picture shows..
If the magnet is not high, try to make small three tight fold.
Glue the cards to the foam plate. Try to align both business cards. (Parallel)
Now, put the plate so the business cards and the magnet stick to the base. The "base" can be a solid cardboard or wood. Anything flat and rigid works fine. I did use a cardboard. Using wood, the sound is better as wood vibrates less than cardboard.