First design the schematic and convert it into board layout, in Eagle layout. Making schematic first helps because Eagle will show you clearly if you make any mistakes with the PCB.
Print the pcb traces out onto semi glossy photo paper.
Then quickly take this paper, cut out your design and place it face down onto some blank PCB board. Then use an iron and press the design on to the board. Use a lot of pressure and ensure all traces of the design make good contact with the blank PCB. Keep it pressed for at least three minutes. After removing the paper you get something like this:
sorry about the flash on image
There are many alternatives for etching liquids, and you can use the one that suits your taste. I use ferric chloride: it’s cheap, can be reused many times, and doesn’t require heating. Actually, moderate heating can speed up etching.
Do not directly heat it, use hot water and put the ferric chloride container in it to speed up the process.
After etching the pcb looks like:
A few drops of thinner (nail polish remover works well) on a pinch of cotton wool will remove completely the toner, bringing back the copper surface. Rinse carefully and dry with a clean cloth or kitchen paper. After drilling your home made pcb is ready to use.
