Refer back to Step 5 for notes about photocopying, but remember this also:
The biggest problem you will run into at this stage is copying the wrong pages onto each other, or in the wrong orientation to each other (i.e. one is upside down). Now is not the time to quit checking your work! Check and triple-check that you have the right pages backed with the right pages, the right way around. Use your imposition guide to check the copies against.