Tutorials are hard, but there are some great writeups like this which discuss some of the specific problems and trial/error involved

https://neuviemeporte.github.io/category/f15-se2

In this case one hard part was trying to get code to compile to identical byte for byte output. Which meant working out which compiler options were used, and which specific compiler too. That gives you a hint of what kinda things are involved.

Have you mentioned this before? I saw a similar context comment maybe 3 days ago on here, down to "byte for byte output [...W]hich compiler options were used"