Your dominant hand (which is the right hand for most people) moves down past your non-dominant hand. The dominant hand whacks the tip of the non-dominant hand a bit while moving downward. The non-dominant hand doesn't move.
less-than, "below that amount," "from there on down"
The left hand doesn't move. The right hand starts under the left hand and moves downward.
The left hand doesn't move. The right hand (dominant hand) moves downward toward the left hand.
more-than, "Over that amount," "above that amount," "exceeding," "above and beyond," "from that point up"
The left hand doesn't move. The right hand starts on top of the left hand and moves upward.
Both hands slice forward. Some people "twist" the hands forward a bit as you see me doing here:
Only the right hand moves. Start with the right hand a bit above and behind the left hand. Then bring (or twist) the right hand forward with a firm stop.
Only the right hand moves. Start with the right hand a bit
This sign is similar to "more than" but the nonmanual marker (body language) is one of a negative headshake, and "ooh" mouth morpheme, and squinted eyes. Also, the right hand travels in a backward arc as it moves upward.