The fastest for me would be a rail fence in 3 or 4 coordinating fabrics. I would strip-piece sets, then cut into squares. After piecing the center I might add a border (or 3) out of remaining fabrics.
A DP9 would take me a little longer (have to create 9-patch blocks, cut them, then reassemble) but it looks complicated.
Warm Wishes is another one that would take me a little longer, but it's really easy to do with a focus fabric and two solid colors.