We sort of play a 4-2-3-1 in defense, which is meant to change to a 3-2-5 in attack. Something like this:
We kind of try to hold that shape as much as possible and interchange positions to cover for others. So, for example, if Shaw is caught further up the pitch, Fred might drop deeper to slot into the LB position and Bruno might drop into Fred's position to hold the shape. Once Shaw gets back, they all get back to their defensive 4-2-3-1 structure.
It's not brilliantly innovative or anything like that, many teams play this way. In the defensive phase we defend with a 4-2-3-1 and see if there's an option for a counter with the front 4 interchanging. In the offensive phase when we have the ball, we try to break down opponents with the 3-2-5.
The problem: For this system to truly work, you need players who will work hard to cover for others and also intelligent players who spot the breaks in formation and position to cover. This is especially the case for the midfield You also need slightly more attacking fullbacks who should be committed to get up and down the pitch quickly. Getting the right personnel for the roles you need is quite important, and we're not quite there in my view. A problem that is unrelated to the system is individual errors, and that's a biggie as well.