Hitting the ball with the bottom of the club face can result from several different swing faults
Focus on your left wrist at the top of the backswing and start of the downswing to get to impact properly, many players have a cupped left wrist which changes the angle of the clubface, this causes an open clubface and results in casting and manipulation during the last portion of the downswing
Using a chipping club with a putting set up will pop the ball up slightly and allow it to land and roll softly which is perfect for when you are chipping down slope and need to kill the speed of your chip