Homebrew PCBs

Thanks. So, as I se,, the light goes inside the box, and the board 
outside, facing down on the light.
I suppose UV light is not good to take.

I just meet a person that uses a fluorescent light tube, and it works 
for him. Just 10 minutes exposure at 10cm. He puts the crystal on top 
of the board, with some weights outside.

I would like to do some test without gettin much into mess. So I might 
try this solution, and if it goes well, then build a proper box. Does 
the box have any special purpose appart from what I said??

Also, if you want to use only a piece of the board. Can you just cut it 
before exposing?? what is best?

Thank you