If you have 20 players and several bags then split into 2 groups, otherwise have one main group and use several balls.
(A) runs and performs a solid tackle on the tackle bag held by a coach with a ball placed on top
Emphasis on getting down low with tackle at hip height - the player should go to ground as a result
(A) must recover quickly and gather the spilled ball. Meanwhile (B) has made good position for (A) to dish out hands without having to turn.
(B) kicks to (C) who is leading towards (D)
(D) marks and handballs to coach once the tackle bag has been reset upright.