Pietrola, cheapest halogen table lamp

Step 3: Making the knots

Wrap the stone with the iron wire making two "knots", one for each of the two wires that conduct the 12v current, the + and the Ground, that obviously don't have to touch anywhere in the total wrapping.
Make the knots in a way that each wire is steadily blocked on the stone, and one of their two free ends is close to the back side, next to the symmetrical and parallel other wire, where they will be connected to the main 12v current wires, and the other end will be the wire going up into the lamp socket.

You can tie them down to the stone as you like it, as long as they will wrap the stone rigidly on the stone base and remain easily movable on the free adjustable part, but make sure you don't short circuit the two (probably almost parallel and symmetrical) wires.