trim size

Book design page size


I have a question about hardcover book design.

If for example designing a 6x9 hardcover book, what size do you make the inside pages, which will obviously be smaller to allow them to fit within the hardcover?

Or do you design the pages at 6x9 and then make the hardcover bigger?

Is there a standard size convention used?

any help would be very much appreciated. Thanks so much!!!