I saw this on her show a while back and luckily I wrote down the directions. Hope I can make it clear.
Let's say you want a finished size 6" 9-patch: Start with two 7.5" squares of your two fabrics (call them A and B). Place them RS together and sew 1/4" seams on two opposite sides (they'll be parallel to each other). Now rotary cut 2.5" from both of those seams. You'll get 2 sets of A & B strips and a leftover strip of both fabrics. Sew one leftover strip to each strip set so you've got an ABA and a BAB strip set. Now place the two strip sets RST, matching the seams and sew the 2 opposite sides which have the 3 seams crossing them. Rotary cut again 2.5" from the seams you just sewed and you'll get 2 sets of 6 squares along with 2 middle sections of 3 squares. Then sew one of those middle sections to each of your side sections in the right order and viola! you've got 2 9-patch squares.
I hope this makes sense. I wish I could add graphics. If I can find a website that illustrates this I'll post it.