The former champions were fourth overall last year after a slow start to the campaign, with Britain's Lando Norris and Australian rookie Oscar Piastri increasingly challenging the dominant Red Bulls.
A new wind tunnel and racecar simulator are now in use at the Woking factory while Rob Marshall and David Sanchez have joined from Red Bull and Ferrari respectively in senior technical roles.
"The preparation so far has been relatively smooth. Smooth in the Formula One sense, which means pushing everything last minute, to the limit. But so far we are on plan," Stella told reporters at a livery presentation.
"So far we don’t see diminishing returns," added the Italian.
"This obviously will have to be proven once we put the car on the ground, but when it comes to the wind tunnel development of this year...(it) seems like we can maintain it.
"We are already starting to work on the further developments that we hope to bring relatively soon in-season and they also seem to be quite interesting."
The season starts in Bahrain on March 2 after testing from February 21-23 and Red Bull will again be the clear favourites, with Max Verstappen chasing his fourth world championship in succession.
Stella cautioned that while confident about the rate of progress, much depended on how much Red Bull had improved their car after the most dominant season on record with 21 wins in 22 races.
McLaren CEO Zak Brown recognised it could be an "unpleasant surprise" when Red Bull showed their true hand.
"I would say Red Bull should be extremely competitive and we will see where we are, what kind of challenge we will be able to set on track," said Stella.
"For us, it’s important that we see we are doing a good job out of our own performance development and we are confident that if we keep doing this, over time we have an opportunity to close the gap."
Norris, 24, will be starting his sixth season in Formula One still chasing a first win but boosted by seven podium finishes last year including six second places.
"When Lando wins his first race it will be a beautiful moment. He is ready for that. It’s more about us being ready and delivering that car that allows him to take the opportunities," said Stella.
"Hopefully we will have the opportunity in 2024."
