The heating pads I bought came with adhesive already attached (looks like they call it PSA pressure sensitive adhesive).
I don't have a single picture that shows the whole setup, so I'll try to tell the story with a few pictures.
Here's the first one:
You can see that the heating pads are wired together, and connect to a white cord. That white cord is just an extension cord that I cut up for this.
Now you can see that the white cord comes from the pads and one wire connects to a relay. The other wire reconnects to the extension cord that plugs into the wall. Had I thought through what I was doing better, I would have only cut one of the wires on the extension cord and put the relay between the two sides of that cut wire. Does that make sense?
One the other side of the relay, a set of wires are connected to a PID controller (it looks like I'm sterilizing stuff in this picture since my temp is set to 180 F). Those wires turn the relay on and off. Another set of wires leaves the controller and connects to the extension cord--those just power the controller. Another brown wire leaves the controller--that's the thermocouple that goes in the milk. I got that from omega, too.
Here's another view:
Is that clear?