Tonight at the store I saw a quilt in the current issue of of Sew Scrappy, it looked like it might be a good lay out for you. It had blocks made of squares 2 blocks across and 3 rows down for each "block" xx
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Then around each block of 6 squares were thing sashing strips (all the same color-theirs was blue). Then a boarder around all of it. Their squares were 2 12 inches but it would work with 3" blocks too. You could adjust your sashing and boarders to get the finished size you want.