With your right hand take hold of your left thumb in the last two fingers of your right hand. Point your right thumb pad at a target. Now make a casting motion at your target, stopping with a pause at the backward movement and going forward to a stop and pause of the forward movement.Just hold on to your thumb through out. Do that back and forward with a rhythm , like false casting,to get the feel.

You can change your plane from vertical to horizontal or beyond those extremes. Just hold on to your thumb.

Rig your rod and lay out about 25 ft. of line and snub the line with your right finger against the grip. Now hold onto the butt of the rod with your left hand fingers through out a false cast or two and let the cast drop to the ground on your target. Just hold onto the butt with your left hand fingers and follow the casting motion of your right hand and arm.

Your right hand and arm will supply the motion. Your left hand on the butt will control a straight rod path back and forward. This is a basic move.

Practice for a while, then let the left hand return to a normal position holding your fly-line with your thumb and forefinger by your left pocket. As you cast back and forth remember to move the left hand in concert with the cast or you will create a belly of slack. Yawing rod movement and slack will not help your casting and I hope this tip will help you with these two problems.