Thank you! I will continue posting things I observe. In the section on https://practicalli.github.io/spacemacs/before-you-start/recommended-command-line-tools.html#locate-files-with-helm-locate, it recommends using fd. However the https://github.com/sharkdp/fd#using-fd-with-emacs suggests installing the "https://github.com/technomancy/find-file-in-project" package. At that point in the book, it is not explained how to install a single package given Spacemacs layers concept. And my initial poking around, it doesn't look like this package is installed by the config you have provided. I am not sure whether this is explained in further chapters, if yes, maybe we can link to there.
@amithgeorge I've removed the hint to install
fd. Initially I thought it would speed up helm-find across the file system, however, using helm-locate instead was much more effective.
SPC p f is another efficient way to find files within the scope of a project, I assume this does the same as find-file-in-project.
I dont cover installing packages directly, as one of the main reasons for using Spacemacs is to use its layer system to avoid the work (and potential conflicts) of configuring packages. There is documentation at http://Spacemacs.org that covers such customisation, so no need to repeat that in the Practicalli book.
I added a page about layers to the introduction which points to this approach as a note at the end.