In the past, McLaren operated a three-person structure with Tim Goss, Matt Morris and Peter Prodromou working alongside each other.
Goss and Morris later left the team, and James Key joined as technical director with overall responsibility for the car.
The new structure has derived from a review commissioned by CEO Zak Brown and conducted by Stella over the winter break after the latter replaced Andreas Seidl as team principal.
As a result, Key left the team and a new structure has been installed with three technical directors working together, namely Prodromou (aerodynamics), former Ferrari man Davide Sanchez (car concept and performance) and Neil Houldey (engineering and design).
Stella insists that the current arrangement cannot be compared with the earlier version.
"I think the only common thing in that organisation and this one is the number three," he said.
"The rest is completely different. At the time, which is when I joined McLaren in 2015, there were three technical directors. I think the separation of competence was very confusing.
"Even for internal people, it was quite difficult to understand, like who was doing what. And the first difference is that now we know exactly what the criteria are for this separation.
"We want in the structure that we have deployed to have clear leadership in relation to the three fundamental areas to make quick cars in modern F1, which is aerodynamics, car concept, and engineering.
"So we wanted to have this model clearly in place as a way of answering the question that Zak and I have shared right from day one, in my role as team principal, how do we create a performance-led organisation? It needed an approach from a modelling point of view to the F1 team.
"The first difference is that, at the time, the technical structure was quite undefined as to who was doing what."
Stella says that the areas of responsibility and now clear, and that the model is also different from the past because the people involved are reporting to a team principal with a strong technical background.
"Now we have a clear underlying model of the team, and more specifically, the technical area," he said.
"In addition to that, at the time, this technical group was reporting to the team principal, who was not technical. Now we have a technical team principal. But I don't expect to be very busy in relation to managing our technical department.
"Because first of all, like I say, we have very strong leaders in each area. And ultimately, what's important is that we bring to the table performance ideas, that's what we miss the most at McLaren right now.
"And when it comes to making decisions most of the time it is a simple, natural derivation of coming to the table with elaborate and high-quality information."
