Taking slower deliberate steps to the foul line, instead of rushing helped me get a much smoother release. Try the
towel method, but be aware of how fast you are getting to the line.
When I first started to bowl, I had very fast feet and got the line way to early, out of control, causing be to drop the ball early,( clunk ) Or speed up my arm causing me to overthrow the ball (loft ). Just My two cents, but by slowing down my feet,it also slowed my momentum towards the line, giving me more control and more TIME to lay the ball down smoothly. I could get lower, because I did'nt have to rush to get rid of the ball.
Hope this makes sense.
Good Luck.!