It's easy to enlarge most 12" patterns to 18" or even a 9" to 18". For 12"--you multiply by 1.5 and for 9"--you just double everything--multiply by 2. You could even take a 6" block & triple it. Try your math with paper first to see if you like the results. Sew it together just like fabric or tape it--remember the seam allowance if you tape it. Less guilt throwing paper in the trash than fabric!