Creating a mask file covering all layers in Photoshop image

I have created an image in Photoshop CS3 consisting of numerous layers including text layers, and graphics layers. The print shop says that I have to submit ANOTHER file which is a "mask" file, which is black wherever there is anything to be (raised) printed on my primary graphic file.

Can someone provide the steps to doing this? I've tried making a mask of individual layers but I think I'm going down the wrong path...