This is a very powerful coaching technique, and one of my favourites to use.
It's both a great teaching tool, but crucially it's also generally fun for players and a good way to deal with large groups.
What is the Constraints Led Approach
An academic definition would be: Manipulation of different constraints or rules to present different information to the learner.
For me, anytime you are changing the size of the pitch, number of players or the rules of the game you are employing a constraints led approach. Despite the way the name sounds, you don’t necessarily need to take options or choices away from player. It's a hands-off way of coaching where you are encouraging your players to figure out their own solutions.
If all you have is a hammer, all the world looks like a nail
Example: Asymmetric games
I previously posted about using asymmetric games as a good tool. When I’m using these what I’m primarily teaching is patience. Ultimate players can struggle to break habits of trying to move the disc forward at all times.
Asymmetric games e.g. 5 offence vs. 4 defence encourage the throwers to take time to look and find the free player rather than rush the disc downfield to contested matchups. However it is important here that you can still score in one pass if the opportunity presents itself.
The key here is that players develop the perception that they should choose to be patient when it is the right choice.
Contrast this with similar intent constrained games where the offence has to throw a certain number of passes, e.g. 5 passes, before they can score.
In this game you have taken away the possibility of looking for a quick score, and thus you've removed the decision making aspect of patience. The players are forced to be patient by the rules of the game, rather than making an active decision to be patient. This isn't necessarily bad - and sometimes this can be necessary to correct extreme habits- but they are less likely to have learned to choose the patient option over the rushed option when both are available.
How to coach using Constraints Led Approach
1. Choose constraints carefully
As in the example above, a really good constraint is one where the player is making an active decision to execute in the way you're looking for, rather than being forced into it.
This isn't easy, so be prepared to experiment, copy other coaches and get better at this through experience. Unless you massively over-constrain at worst you are still going to be running some fun and challenging games for players to run, throw, catch, defend so they really can't go too wrong.
2. Question before direction
If players changing their behaviours in the way you're looking for it is going to be tempting to jump in and telling them what to do. Resist this urge for a while. If you're looking for changes in behaviours it will take a number of reps of experimenting before players start figuring things out and organising.
Once you've given time and are still not satisfied your first intervention should be a question: how do the players think they should approach this problem? Quite often you will find that someone actually has the right idea already but was too shy to take charge on the pitch. If not, well-directed questions can help guide them towards the solutions.
3. Be Open minded
One of the reasons I like using these games so much is that it allows players to come up with solutions which may be different than the ones I had in mind. The most efficient path to improvement in your team is to work with them and their inherent abilities, rather than always trying to impose your ideals onto the group.
Sometimes these solutions the players come up with are impractical in real games - but that is always feedback for me that I designed the constraint badly, rather than the players are wrong.