Lay out the grape leaves on waxed paper.
Pat dry with paper towels, and set the wick on waxed paper to cool completely.
Place the assembled puzzle on top of a piece of thin plastic or waxed paper to prevent it from becoming accidentally glued to your table.
If the leaves aren't perfectly flat, you can cover them with waxed paper and put a heavy book on top of them for a day or two.
However, cardboard, poster board, or waxed paper work just as well.