Once you have a properly configured environment and a brand new configuration file, you just need one single command to start the building process. On your terminal emulator, in the kernel source folder, launch:

$ make

The make command will wrap up the necessary configuration and will launch the compiling and assembling process. The duration of the process heavily depends on the performance of your system: it could be one minute or one hour. As a reference, an i5 2.40 GHz CPU with 8 GB of RAM takes 5-10 minutes to complete a clean build. This is incredibly quicker than compiling the whole AOSP image, as you can see, due to the different complexity and size of the code base.