The ones I made included a CCF sole. This is the smaller foot-shaped part. I sandwiched that between an inner and outer sole fabric cut from the larger foot-shaped piece and sewed around the edge. The smaller upside down U-shaped piece is the top of the foot shell. I sewed a 2.5" wide strip of thicker reinforcing material around the outside edge of this similar to those MEC Hut Booties in the web address above. (BTW - how do you make that into a link??). The rectangle is the ankle/calf section. This gets sewn to the inner part of the upside down U. That's the shell.
For the inner liner, I used the larger upside down U, and stitched the notches at the top closed to give it shape. I did the same with the insulation, which was either .75" or 1" thick (leftover from a Ray Way quilt). If you didn't want the reinforcing bumper strip on the shell, you could use this shape for the shell too. The dotted line on the rectangle and large U shape is where I removed 1/2" from the edge of the insulation and then basted the two pieces of insulation together. Stitch the rectangle inner to the U-shape inner; then the inner upper is complete.
From there I made the sandwich of inner, insulation, and outer, and put it all together. I included a drawstring at the top of the calf section that exited at the front. It took a little bit of wrestling to get it under the sewing machine with the foam in the footbed, but it was manageable.
This is the pattern from my girlfriend's pair. She has size 7.5 feet and they fit just right - not sloppy, but not compressing the insulation. I haven't gotten around to making my pair yet, and when I dug out the pattern I realized I don't have all the the pieces together yet.