What does "Bottom of the Circle" mean to you? I'm sure it has all sorts of meanings, but to a golfer, it should mean "where the club bottoms out".
So, if we think about it in that context, shouldn't that be where the club impacts the ball? Would that possibly be where you would want your ball position to be? Is it the same for every golfer? Let's answer these questions.
Yes, the bottom of the circle would be where your club first hits the ground or in the case of a long iron, hybrid or metal wood, where it becomes level with the ground.
Yes, this is where you want your ball to be, so that it gets the best impact and where the club face is square at impact.
No, it is totally different with every golfer. We are not all built the same, so it has to be different.
How do you find your bottom of the circle? Head down to the local driving range, get some stretches in and hit a some balls to get warmed up. Then get out your favorite iron and take a few swings to see where it actually hits the grass first. Now, put a ball down and see if this is your normal ball position. It may or may not be, but trust that you just did the drill to find the bottom of the circle. Hit a few shots with this ball position. You should hit the ball better, and yes, it might take a few more swings to get the feel of the new position. Now, switch to a longer club and do the same drill. You should start to make better contact with the ball, no matter what club you are swinging. Swing all of your clubs to find the bottom of the circle, you might be surprised that you had the ball in the wrong position. Believe me, the ball doesn't have to be out of position much to make a big difference.
I hope this helps you make better contact with the ball and hit more consistent shots. Have a great golf week.