My tips comes from 3 librebooted X200s I’ve done (plus 1 fried due to user error by me):

• your most important tool is a heatgun with smallest possible nossle (or is it nozzle?)
• replace the stock WSON-8 nightmare chip with 8 mbit SOIC-8 chip
• take a photo of red dot on the WSON-8 before heating it, it shows you the right position/angle/side for the SOIC-8 chip too
• be aware that the whole bottom part (i.e. big area) of that nightmare WSON-8 stock chip is soldered
• do not compile libreboot with raspberry pi nor any sbc you’re using (use real x86 computer)
• when flashing, use slower spispeed than you’d use with Coreboot (older machine)
• soldering the SOIC-8 chip do not require any skills nor good vision (super easy task)

With a good and especially small nossled heatgun you don’t need to cover the motherboard at all. If you melt the plastc top cover of the WSON-8, it doesn’t mind but not necessary either. Just don’t melt the motherboard (small nossle!!!) and you’re all good. Use tweezers rather than pliers, because force is bad and when the super-high quality soldering tin is melted completely, the WSON-8 chip comes off even if you just blow on it.

Flash the 8 mbit SOIC-8 before soldering it onto the motherboard.

I have no lots of soldering skills/experience, but it is fairly easy task if you just have the small nossled heatgun.

And oh yeah, some guides suggests to solder jumpwires onto the stock WSON-8 chip rather than heating it off, but that approach was way too hard for my soldering skills even with the smallest possible tip on my Pinecil soldering iron.