It's a breadboard with an extender for a Raspberry Pi's pins flipped upside down, a Raspberry Pi Pico, jumper wires, and a clip that came with a CH341A that suffers from the issue of being 5V.
The issue I think would be length of the wires.
Any thoughts? I'd consider soldering something together but I don't have a soldering iron that would be great for something so small and I'm working with what I have on hand.
I also have a Raspberry Pi 4 and the CH341A that has the voltage issue if anyone has a better idea that might work.
You should check whether Pi Pico is supported by flashrom.
If it's supported, then you can flash. At the end of the day, your BIOS doesn't care how it get in there.
Could errors during the flashing process be dangerous though or would it just mean trying again until it works?
You are flashing the chip directly so apart from inadvertent short circuits and such if it doesn't work you can just keep trying until it does.
As for wire length it all depends on how fast they clock the SPI bus when flashing. You'll probably be able to get away with 20cm or so without difficulty , I've driven SPI displays with that kind of wire length before.
What kind of errors?
Have you read successfully at least? By that I mean getting consistent dump.