Double sided home-etched PCBs require a lot of patience and luck. Both sides need to be aligned properly, and via wires have to be soldered between the layers so top and bottom are connected.
The usual process for connecting the layers is to insert a small wire in each via hole and solder it. This is a tedious, time consuming process. YourITronics documents another way: thread a long wire through all the holes, solder it in place, and cut away the excess. The result, as seen above, is a very small, very clean via connection. There’s even a few under the TQFP chip! We’ll definitely use this tip the next time we make a double sided board at home.