I flashed my Lenovo x230 with Coreboot and documented how I did it.

This procedure has a good amount more steps than the Libreboot X200 Flash. Mainly it is due to having to build and configure Coreboot & friends.

I urge you to check the sites I list below and cross-reference them with my information. I may have some typos and the people who wrote them are probably a lot more knowledgeable than I am when it comes to this stuff. I am good at following directions and figuring things out, then documenting it.

Main bit of advice here is to read over the directions once before proceeding then once you start, go slowly!