I then figured out how I wanted to put the squares and the pattern I was going to use. I put them in chronological order starting with freshman year shirts at the top and then worked my way through the years, ending with senior year shirts on the bottom two rows.
I put a 12x12 square and then 2 6x6 squares stacked on top of each other. Alternating the start of each row with either a 12x12 square or 2 6x6 squares to make a neat pattern.
I used interfacing to make the squares a bit stiffer and easier to sew together.
I sewed two 6x6 squares together then sewed the 12x12 square to it and continued down the row.