This is a very useful tutorial and I have a couple of updates/suggestions. Since kernel version 4.14 (I believe) the package "libelf-dev" is also required to compile. And with the package "debhelper" installed you can instead use

make -j 6 deb-pkg

to create a set of .deb packages to install, rather than using the make install steps. This makes it easier to copy your newly built kernel to other computers, or to uninstall it.