I'm far too lazy to find the website where we found the instructions for impregnating the fabric with wax, but I will show here how it was done by us.
The first step is to cut a piece of craft paper, or a brown paper bag, and aluminum foil at least as long as the piece of cloth, and at least twice as wide. You want to be able to fold the foil and paper like a soft taco to with the foil and paper in lieu of tortilla, and the cloth and wax in lieu of delicious taco meat. MMMmmm tacos....
The next step is to evenly spread wax shavings on top of the cloth. We did this by using a crappy steak knife to scrape wax off of the big block and onto the cloth.
Next fold the taco... I mean foil and paper around the cloth and use an iron on medium heat to melt the wax. We found that if you go very slowly it gives the cloth time to soak up the wax and impregnates it more evenly. Quickly remove the cloth and allow to cool. Voila! Waterproof fabric that won't leach death into your food.
Up next... Adventures in sewing