I've created two individual parts. I need to have the two interface with slots created on one part by the other. I plan to use Combine > Subtract to do this.

However my issue is that the two parts are not orientated correctly; they are out by either 90 or 180deg on two different axes.

How do I rotate one or both parts in order to have them mate correctly so I can successfully create the slots? Each part is made up of numerous sketches/features, so I need to rotate the part as a whole.

Thanks!