Well, not much to elaborate over. When large panels are made/assembled, there's often a bit of "scrap", from fitting and from the *ooops slippery* incidents. These can be used by assembling equal size bits (or parallelling smaller sizes - just remember that the weakest cell, current-vise controls the max current).
A few smart companies sell all the chips and it's good for many hobby purposes (don't have a link handy, I just see them every now and then).
eBay is another possible source of course:
40 Barely Broken 3X6 Solar Cells Photovoltaic Panel
US $38.50 + US $6.50 shipping (I would get a set myself, but he only ships within the US and Canada).