The documentation here...
to a build setup that AFAICT is different to the reference application,
which I think is here... https://github.com/seL4proj/sel4webserver
The build setup of the reference webserver application is the same as the "kernel
directory" setup in the documentation.
It looks a little different as the reference application is just one component of the
entire reference system.
If you scroll down a little in the webserver GitHub link, the repo init and repo sync
commands pulls the required components of the webserver reference system and organises the
components into a directory structure that's similar to the one listed in the
"kernel directory" setup in the documentation. The contents of the sel4webserver
repository can then be found in the 'projects/webserver' directory after the
repo sync command.