I have a PCB which has the perfect size for a project of mine, so I would like to use it if possible. However, the copper plating on the back side of PCB only surrounds the individual holes (that is, no holes are interconnected). See picture right here:
I find this strange. How can this be useful? I would definitely need some copper tracks with interconnected holes in there because some components need to be connected to each other. Am I supposed to make my own tracks somehow?
I saw some stuff online about people who would insert multiple wires in the same hole to make interconnections, but this seems undesirable. I'd rather avoid that if there is some way to make tracks.
Clipping before soldering leaves a smaller solder blob than otherwise. 
Best Answer
What you've got is called a prototype board. It is available at electronics suppliers everywhere and is obviously not meant for production. Join things together any way that is convenient for you. Many methods have been pictured. Another common way is inserting a component lead beside its next connection and just bending it over to fit.
The results are typically quite messy, but it can take a lot more handling than a breadboard prototype. Thus it is a common step before getting printed and etched boards made.
You can also find prototype boards in the same circuit pattern as the push-in breadboards, so you can simply transfer your circuit from one to the other, solder, and install.