Setup. Keeper in goal. A server at the corner flag. Flat markers on the goal line at the near post, the middle and the far post.
How it runs. Walk it first. The keeper sets up for the corner and freezes, and the group checks the position: middle of the goal or just towards the far post, a yard off the line, body half turned so they can see the taker and the box. Then the server delivers: one to the near post, one to the middle, one to the far post. The keeper claims what they can reach and calls "Away!" for the rest.
Make it harder. Add attackers and defenders who stand still. Then let them move. Then use inswingers and outswingers and ask the keeper how their start position should change.
With 4 keepers. Keeper, server, two attackers in the box.