What is the width of fabric? If it is 60", use a multiple of 60. Ie 10", 6", 5", 12"...for your circle diameter or block size. You could use the edge pieces for half circles, if need be. If you want to play around use large piece of paper, freezer paper. Wof and say wide enough of three or four rows of blocks. Lay the shapes out and find the most efficient layout. Read on other thread to buy rolls of paper at hardware store that the painters use to cover windows, big enough and cheap. This would be the way to start, you could figure overall size once you know, wof, how many you can get in the size you want.