In short, you don't. You can group the layers into a set, that may get you the result you want. Or maybe not, it depends on what you need to do.
Another way to go is to make a copy of your document, turn off all the other layers, flatten the doc, then copy the layer over to the other doc. The downside is that you'll lose any transparency in the layers, but you can always bring it back again (hint: make a mask and save it as a path first).