I have also done this "procedure" a few times in the past with mixed results, But from what I remember, Here's How I did it:
If you want to Test this procedure First, Try it on a piece of other non-working hardware (PSU, Graphics card, etc...) just to see when the PCB solder starts to Flow.
Remove the CPU, heatsink & fan, RAM, BIOS battery, wires, speakers, stickers, plastic sticky guards, foam spacers, absolutely everything that can be removed from the motherboard. .
It is also a good idea to wrap additional foil around the more sensitive parts of the motherboard, like areas where there are Capacitors, PCIe sockets, RAM sockets, Other plastic non-removable parts and the CPU socket.
Place the MB (CPU Side Up) on balls of tin foil (between half an inch to an inch wide) on a baking tray.
Place the baking tray with the motherboard on it into a preheated oven at 200C / 385F.
After 8 minutes,
turn the oven off and
open the oven door.
Do not remove the motherboard from the oven at this stage as You may disturb the still semi-liquefied solder. Take care not to inhale any fumes that might be present.
After 20 minutes to half an hour, remove the cool motherboard from the oven and begin re-assembling. Hopefully, The problem is corrected and It will Boot up again.
If the problem remains, you could try the procedure again, leaving it in the oven for a couple of minutes longer or at a higher temperature.
It'll either work or it won't, But Nothing ventured, Nothing gained.
You could look on the Internet to view some actual Videos of this procedure before attempting this, But that is up to you.