Warm a flat sheetpan in the oven.
Using an offset spatula, spread the melted chocolate in a thin, even layer on the warm sheetpan.
Place sheetpan in the refrigerator to cool.
When chocolate is firm, remove sheetpan from refrigerator. Holding a dough cutter at a slight angle, push forward over hardened chocolate. They will curl only at the correct temperature. If they don't curl immediately, you may need to either put the sheetpan back into the refrigerator or let it sit at room temperature to warm up.
These are tricky and take a lot of practice and patience.