My dh wanted to make them because he keeps bees and had lots of wax. The first attempt came out too stiff to really use. The second was better, but not quite there yet, so I bought a pair at Trader Joe's. I used them a couple of times for dh's sandwiches but I don't know where they are now. (He probably left them at work, or it could be in the lunch box he lost.
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All the wraps I've seen have beeswax with added pine resin. (That's what was on the Trader Joe's wraps I bought.) We think the resin is what gives it flexibility because dh didn't use it and his wraps were stiff.
There are two methods for making them. One beekeeper we know melts the wax and dips the fabric. Another irons grated wax into the fabric. You don't have to hem the fabric because the wax keeps them from unraveling. Most people just cut the fabric squares with pinking shears.