Just go through FIle > New > Business Cards and select your sheet stock, then delete whatever you don't want. Save the blank as a template (File > Templates > Save) and you can use that to make whatever you want: File > New > Templates and Documents.
That will always assume that you want to make a sheet of cards, all of which are identical to the first one (i.e. the top left). If that's not the case, then unselect the "Synchronize contents" option in the business card dialog.
acknak, what do you mean "delete whatever you don't want"? How do you delete what's in a template? Do you mean template as you only mention selecting sheet stock? Please go step by step assuming the reader doesn't know as much as you do.