4-patches with the 4" squares.
Or use one 4" square as a base and use another 4" sq. - cut into four 2" squares as "snowball" on the base. The resulting shape will be "roundish" when you sew several together. And the snowballs int he corners of several blocks will make a little quarter-square triangle block.
Cut the 4" squares in half and make a piano-key border.
Jan in VA