Building a FreeWRT firmware image is just like building a new Linux kernel, but a little more complex. There is a ncurses-based configuration menu at the beginning, the changes made are saved into a file named .config in the ADK root. The build is done by the various Makefiles, compiling and linking the sources together accordingly to the symbols defined in .config.
Unlike kernel compilation, FreeWRT needs to be cross-compiled. This leads to special premises, as most of the tools need to be specially build. But no panic, FreeWRT will do this all for you. In fact, this is done at the second run of make (the first one opens the configuration), and therefore can be seen as part of the first firmware build. For clarity though, we will discuss these two things separately.