For extra absorbency for older babies, I fold a second flat into a narrow rectangle. (greenmountaindiapers.com)
The Nighttime Training Pants add extra absorbency for overnight protection. (earlymomentsmatter.org)
You simply fold one diaper and place it inside another in the area baby needs it most (boys need extra absorbency in the front and girls need it in the middle.) (diaperjunction.com)