Solder a couple wires onto the two solder pads. When you're ready to do the BACK flash BIOS update twist the two wires together (shorting them) the required amount of time, then untwist and let the flash commence. When done, reboot into BIOS. Once you know you can do that then do all future BIOS updates the recommended way: through M-Flash.
Then cut the wires off and cover the hole with a deadhead sticker.
A back-flash update is really only a once-in-the-lifetime (of the board) thing and you don't even really need a switch.