I actually use the same method as Jape, and just let gravity pull the sheet down onto the wax when the wire is heated up. I used to have an embedder like Jeff's but left it with my hives when I moved. It takes some accurate timing so the sheet doesn't melt through if you haven't got a waxing board. Some gentle pressing at times (when the cables are diconnected and the wire is still hot) help get uniformity. After a couple of attempts it's pretty straightforward.
I'm not encouraging anyone to use a battery charger.. but that's what I use (have had chargers in the past that fail to work)
That's probably the worst one out of a batch I did today.. not sure why I decided to photograph that one!
While i'm giving away secrets, an unused rivet is perfect for inserting brass eyelets before wiring the frame!