thank you all for the comments. I really needed a large space to lay it out so I didn't have matching colors next to each other so I waited until a day i could spend at my sisters in her sewing "loft" (her entire second floor is one big room with little nooks and crannies and it is almost entirely filled with sewing stuff!) I used just two layers of flannel -one for the front and one for the back. the back is solid black. i wanted something that would highlight the squares and with so many colors in it i thought black would be the best choice.