Yes you should. OK, you can get away with a little push under the ball with a lob wedge when close to the green and only want the ball to pop a few feet and stop, or like you explained to roll down a slope but it's still risky. Hitting under the ball has a high chance of catching the ball with the leading edge and thinning it across the green. Hit down on it with an accelerating blow, by varying the club, length of back swing and follow through you can chip the ball anywhere with control.