Yes, it's simple. The diagonal of a 10" square is about 14" so the outside edges of the HSTs would be more than 6".
BUT the reason I do not recommend this method for HSTs is because the resulting HSTs have bias edges along their outside edges, yuck!
Try cutting your basic squares at 10" -- or maybe even 10.5" -- draw a diagonal line in each direction and in half thru the middle both directions.
Sew 1/4" away from those two diagonal lines, on each side of them. Then cut on the drawn lines. Press and trim.
Jan in VA