I keep rolls of fabric strips, ranging from one to two inches wide, in a box in my sewing room. In another box, I keep 12 inch squares cut from newspapers.
Every day, or every two or three days, I sew a few strips onto the paper squares, diagonally, starting in the middle. Light colors on one side, dark colors on the other side. I wait until I have a pile of 10 before I trim them all to the same size and tear off the newspaper. Sewing one block takes about 10 minutes.