I woulI would rather recommend you to buy a transformer than making it. The cost to incur is more when you try to assemble one and this excludes the errors that you might encounter during the test.
I supose he didn't think about building/making trasformer.. It's just about desinging it using some software, try to google software for designing transformer.. There are probably free / trial / demo versions around..
More interesting to me is, what do you need this transformer for??