This should work on any ASUS motherboard that supports BIOS Flashback. There should be a button on the back panel if yours does. You can update the BIOS without the CPU installed with this method. You do not power up the PC at any point when doing this.
In this video, we show how to update the BIOS on an ASUS motherboard using the BIOS Flashback method. This should work for most ASUS motherboards including Z790, Z690, B660, H610, Z170, X299, X570, B450, X670 etc. Pretty much any Intel or AMD motherboard that supports BIOS Flashback. Just be sure that you download the correct version of the BIOS for your specific board.
Find your motherboard BIOS here:
Some supported motherboards:
ASUS ROG MAXIMUS Z690 HERO
ASUS ROG CROSSHAIR X670E HERO
ASUS ROG STRIX Z790-E GAMING WIFI
ASUS ROG Crosshair VIII Dark Hero
ASUS ROG STRIX B660-A GAMING WIFI D4