http://wiki.friendlyelec.com/wiki/index.php/How_to_Build_Fri...
In general I agree, it is pretty nice. The thing I'm struggling with right now is getting kernel config right as I'm attempting to do a build with 6.0 but the configs from OpenWRT-5.15 do not work directly with that (or I'm doing something wrong...). The difficulty is that the kernel config seems to be done in layers in a way, assembling and the merging the final config from different sources and its not completely obvious where to poke to make it work. I don't think its insurmountable, but just takes some effort to figure out the build system etc. Especially as I'm trying to do things the "right" way instead of just trying to patch up something bootable.