There's probably lots of ways to do this but here's how I did it. Early days, and if I find any wrinkles or better ways, I'll blog and let you know.
Needless to say I used a gelli plate. I think it should be doable with other forms of monoprint too.
Here's a step by step of how it was done.
Choose your magazine. Not all will print apparently so you may need to try a couple of times. This is a BBC history magazine and was perfect. Cut out the image exactly.
When you're sure the paint is dry, put a contrasting colour of acrylic paint onto the plate. You will need a thin layer, so don't use too much. Keep cleaning the brayer on a spare piece of paper if you have too much - don't try and scrape it off.
It should look something like this - a nice thin paint layer.
You're now ready to print. Lay a piece of paper over the top of the paint and press firmly all over (burnish). In the photo below I wanted the print in a book so it was easier to lift the gelli plate onto the book page. You need to press quite firmly doing it this way, but it helps if you keep the plastic sheet that comes with the gelli plate on the bottom - makes it easier to rub.
Here's the finished thing again. I printed on top of a coloured base but it would be even clearer on white paper.