On the copy of basic block with darts, adjust the length first.
Make it to the ground on front and 30-40cm longer in center back if you like a short train.
On front, from high point shoulder draw the new armhole/neckline ending on side seam 5-7cm below armpit.
Draw also the neckline from high point shoulder up to 3-4cm above waistline.
Still on front, flare at hem maximum 15 to 20cm on side.