First I cut each handprint into a square or rectangle 9.5" or less.
Then I cut strips of varying widths of the different fabrics I had. With them I started making up the difference so that each block would be 12.5" square. I wanted to have some striped borders also and sewed many strips together, then cut them into 2" wide strips.
I'm using the back of a tablecloth as a design board. It's perfect.