Just recently a guild member approached me on how to do this...I did a search and found these videos.
https://www.youtube.com/watch?v=KvCEL3_CNlI
https://www.youtube.com/watch?v=BkDnJzJv87s
There are other patterns you could use...my friend had different colored bags and the Fship star design worked well with them. She made 64 12" blocks for hers with a 4" border made from a purple grunge fabric so was about 104 x 104