I THINK you misread the directions. (I suspect your "make prepare" was actually "make mrproper", The "mrproper" target is a "delete all configurations, temporary files, and intermediate files, leave source code as a totally clean installation of source").
If you have a installation and a pre-existing configuration file, then the following can be used:
make menuconfig - this will verify your configuration file, remove options that
have been deleted, AND query any new options that were not defined
(I suggest taking the default offered on these - it is very rare that
any have to be answered other than the default).
make - this will build the kernel
sudo make modules_install install
--- this does the of installing driver modules, AND installs the kernel,
creates the initrd (with drivers)
This information is in the "README" in the root of the source code.
side note: (and this is documented somewhere, not sure where though) The term "mrproper" is European and is a play on the "Mr Clean" US based cleaning and sanitizing kitchen detergent product used for cleaning floors, counter tops, sinks... The "Mr Clean" usage was restricted in Europe (already used for something else). It is used the same way a "make clean" is used.