Step 3: Wrap Magnet in Foil
Wrap tightly, then pinch the ends closed. Don't pinch tightly or the foil will tear at the corners as they are sharp. The excess at the ends can be torn off carefully, or cut with scissors, leaving 1mm or so overhang that is then folded down and compressed.
To cut with scissors: grip magnet tightly in a fist so that the edge of the magnet is 2 or 3mm below the thumb-side of your closed fist. Rest the scissors against your hand...you will feel the magnet pull the scissors tightly against your hand. Keeping a firm grip on the magnet, angle the scissors slightly up so as not to cut any of your skin; cut the aluminum.
(Use this same technique for cutting the excess duct-tape in Step 6.)
*In this picture I'm a little too close to my clipboard...moving that magnet 1cm to the right would cause an unwanted attraction.