Draw your designs
First thing you want to do is get a sketch pad and a fineliner, fineliners are the best for this sort of thing for one reason, as i tend to put it "they do what you want them to" in this case they are good as they can get the scale right, a biro or other ink pen would just be way to large! With your tools in hand you want to mark your "boxes" down and start filling them with newspaper shreddings, wanted posters and adverts.
As you can see i also did one "random" scribble on the bottom left, this was an experiment to see if it would translate as posters once i cute it all up.
Beige it up!
So now that you have your designs done you want to water down some beige or bone with a 3:1 water :bone mix. after that you want to simple rub it ver the designs once. relatively quickly. don't be too picky and don't let the water pool.
CUt and glue baby!
Cut them out and stick them on! if you feel like it at this point you can use a slightly darker tone (as i have above) to level out the beige to match your terrain better. If you want to go the extra mile you can black line the edges, although i do not think this is necessary.