For small projects you can get away with :serial t if you have a fairly straight forward set of file dependencies.
:components ((:file "package")
The most interesting part of the article though was the description of your approach to development. You never write top-level forms, always writing definitions instead. You use the REPL for inspecting stuff.
I tend to use the end of the current file I'm working on as a scratch pad full of top-levels while developing. As I get each form ironed out, I move it into a definition above the scratch pad area. It feels like molding a piece of clay into a vase and then setting it aside for firing. I almost never use the REPL in SLIME except to load system definitions, restart Lisp, change directories etc.