I am an engineer at a solar plant. We start from bulk silicon, make the wafer, then the cell, then put the cells into panels. Yes, the basic idea of making panels is simple, but you cannot make your own cells without some very expensive equipment (even on a small scale) and the ability to purchase some nasty chemicals.
As for the panel assembly, there are many details that need to be worked out to make a robust, efficient, and weather-proof panel.
Let's keep in mind that the most expensive part of the panel is the silicon. And, if it were really that easy and inexpensive don't you think the manufacturers would do it for less? As an industry we still have not reached grid parity on the basis of cost. That is why you don't see panels on every building.