Just made one tonight been so long since i done this but it was great fun.
What i did was got myself a second hand pc chips 810lmr rev7.1 motherboard it has a 256k 32pin dip flashrom windbond W49F002U-12b, slapped it all together to get into dos with a keyboard and floppy.
first i made sure bios cache was enabled.
got myself uniflash and the bios i wanted on a floppy i used m8plus 256k.
booted to dos and backed up the motherboad bios, then i burned the xbox bios to the flashrom.
I left the pc running while i removed the chip then soldered it into the xbox with a corrupt bios.
flashed the tsop on the xbox then removed the chip stuck it back in the pc and flashed the motherboard bios back.