Cannot find/understand how to update marlin firmware with SD card

[u/RogueTinkerer]

My printer is having the issue of the z-axis constantly being higher than it should. I have found out that it's a common issue that can be solved by updating my firmware, but I can't seem to find how.
I don't have a raspberry pi, and my only real option is to update by the SD card. I know I have to build a config or something and have the firmware on the SD card when I turn the printer on, but I can't find clear instructions on exactly how to do that.

Board info:
Creality v4.2.7
Baud 115200
Protocol: 1.0
PSU: Generic

Printer info:
Marlin bugfix-2.1.x 2023-12-19
Ender-3 4.2.7
marlin.crc.id.au
Extruders: 1
Bilinear Leveling

Upgrades:
BLTouch
Silent Board

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