you have all choices, if you want to elaborate on specific design characteristics, you could build on bread board, with minimum soldering but think what happens when it gets bumped... or go as far as doing custom pcb and solder all your components... plus think of enclosures and mounts....
for you since this is for a common solution rather than a learning project i would recommend going with prebuilt, its better quality and prolly more reliable, the only thing to watch for when buying is that all the specs meet your criteria.
thanks for the replies. I would want something that can make things run for second and minutes. looks smart neat and tidy and cheap also fit it in to some sort of plastic casing. And simple to use
I would get a metal electrical box to mount the timer in. Buy a short, heavy-duty extension cord, cut it, strip it, and you will have a male and female plug and socket...