Because of the many variations of foot placement by golfers: toes perpendicular to target line; flared out one way or the other; or both, the best way to gauge the alignment is from the back of your heels.

Place a club on your target line near the ball and an additional one against your heels and you will see your true foot alignment. Make the necessary adjustment with your feet to parallel the two clubs. Practice this way several times and you should get used to the look and feel of being square to the target line .
good luck, Bob