Prepare your outer PUL fabric as usual (adding snaps and/or hook & loop.)
For your inner, you will need a non-absorbent full layer of something like suedecloth, poly fleece, minky, etc. Plus 2.5-3" tall by the full width strips of PUL for across the inside of the front and back. The absorbent soaker flaps will need to be the length you would use for your Small size soakers and not very wide. They can be topped with a stay-dry fabric or be left with a natural fabric surface. Mine are each 2 layers of heavy hemp/cotton fleece with a bamboo fleece layer on the top.
Center and align your soaker tops with the tops of the PUL strips with the shiny side up.
Sew down the top of the soaker securely to the PUL strips.
Showing the underside. Sew with this side down.
Flip to PUL up and pin/clip your PUL+soaker to the inner body panel.
Your inner is now all sewn together.
I pin down my soaker flaps so they don't get in the way of the rest of the sewing.
View of the underside.
Clip your inside and outside with faces together, and sew together like with any other diaper.
Front left open for turning:
Trim your corners before turning.
Turned outside view:
Turned inside view:
Sew your elastic casings, install your elastic, and top-stitch to close up your turning hole.
All of my free diaper pattern templates can be downloaded here: http://prefold2fitted.blogspot.com/2012/10/online-free-downloads.html