If you want your fussy/focus square to be 6" finished, cut it 6.5" square.
Cut your strips for the 4-patch squares to 3.5". Sew strips together and cut them crosswise to 3.5". Sew 2 of those together for your 4-patch.
This pattern is used by Quilts For Kids. You can order a free kit to assemble and return to them as a finished quilt. Go to www.quiltsforkids.org for more info.