Since you are talking about returning a lob, I assume that you are referring to the "
tweener" trick shot (back to the net) rather than a half-volley shot played between your feet while facing the net.
I find that the
continental grip works best for me to execute the tweener. While chasing down the lob try to get in line with the flight path of the ball so that the ball bounces a few feet (less than a meter?) directly in front of you. Once the ball has bounced you need to catch up to the ball before the 2nd bounce. Just before the ball will bounce a 2nd time, you need to be directly over the ball in order to play it successfully.
If you don't get past the ball, I suppose that you could execute a tweener-like shot on either the left or right side of your body instead of between the legs. If you can outrun the ball, then spin around quickly and drive the ball with your forehand -- not quite a slick, but still impressive if you can hit an aggressive shot back rather than a lob return.
If the ball bounces high enough, you can drive (or lob) it back with an
over-the-shoulder shot. This was discussed recently in posts #30, #31 and #35 of the following thread:
tt.tennis-warehouse.com/showthread.php?p=2465141