The Trident driver, who joins the team from Hitech Grand Prix for his third season in the series, set a 1m48.012s to top the timesheets on Friday morning.
Rookies Saucy (ART Grand Prix) and Franco Colapinto, driving for new outfit Van Amersfoort Racing, had been trading times at the top of the timesheet before Stanek took the top spot with 15 minutes remaining of the sole practice session.
It is the first time the series races at Bahrain International Circuit, having undertaken its pre-season test here earlier this month.
Ferrari Drivers’ Academy member Leclerc, who had been sat in P8, went second-quickest with seven minutes remaining of the session, setting a 1m48.090s, before he was pushed into third by reigning Formula Regional European champion Saucy.
Leclerc’s Prema teammates also finished in the top seven, with fellow FDA member Ollie Bearman and Red Bull junior Jak Crawford in sixth and seventh respectively.
Prema, the reigning drivers’ champion with with Dennis Hauger, will be hoping to clinch the teams’ championship this year after being narrowly beaten by Trident last season.
F3 has just one practice session ahead of today’s qualifying, with the new format seeing one reverse-grid sprint race on Saturday and a feature race on Sunday.
Alexander Smolyar went quickest 10 minutes into the session as the first representative laps were set, leading an MP Motorsport 1-2-3 with a 1m49.458s from Kush Maini and Caio Collet.
The Russian driver had previously said he would not compete in F3 or any international racing this season as sanctions were imposed on drivers from the country amid the war in Ukraine.
But he appeared on the series’ entry list for this weekend as an Authorised Neutral Driver under the FIA flag.
As the times ramped up, Juan Manuel Correa topped the timesheets with a third of the session’s running complete, setting a 1m48.642s to go four tenths clear of Colapinto as the first driver to break the 1m48s barrier.
The ART Grand Prix driver returned to racing last season having been forced to sit out 2020 after suffering horrific injuries in the FIA Formula 2 crash at Spa in 2019 which claimed the life of Anthoine Hubert.
Teammate Saucy was the second to head into the 1m48s, slotting into P2 just 0.05s behind Correa.
He traded spots with Colapinto, who briefly went quickest, before regaining the top spot with a 1m48.099s.
Reigning champion Prema was late out the garage, with its three drivers only emerging from the pits with 20 minutes of running remaining.
Bearman and Crawford went fourth and fifth respectively on their first flying laps, with Leclerc slotting into P12, before managing to move up to P8 on his next attempt with a 1m48.681s.
Isack Hadjar, who led the second and third days of the pre-season test, went seventh fastest for Hitech on his first flying lap, setting a 1m48.665s.
Just one second covered the top 15 with 15 minutes remaining, with Stanek going quickest with a 1m48.012s.
Much of the field headed into the pits for a brief break before heading out for the final 10 minutes of the session.
There was a brief yellow flag in sector 1 as Reece Ushijima came to a stop on track, but he was able to get the car going again without causing much disruption to running.
Victor Martins, the highest-placed returning driver from last season, only managed P12. The Alpine Academy driver joins ART from MP Motorsport this season.
Collet, who also enters his second year in the series, put in 18 laps, the most of any driver, but ended up in P17 having been near the top of the times earlier in the session.
Bahrain F3 - Practice results:
| Cla | Driver | Team | Time | Gap |
|---|---|---|---|---|
| 1 |  Roman Staněk |  Trident | 1'48.012 | |
| 2 |  Gregoire Saucy |  ART Grand Prix | 1'48.036 | 0.024 |
| 3 | Arthur Leclerc | Prema Powerteam | 1'48.090 | 0.078 |
| 4 | Isack Hadjar |  HitechGP | 1'48.285 | 0.273 |
| 5 |  Franco Colapinto | Van Amersfoort Racing | 1'48.402 | 0.390 |
| 6 | Oliver Bearman | Prema Powerteam | 1'48.419 | 0.407 |
| 7 | Jak Crawford | Prema Powerteam | 1'48.428 | 0.416 |
| 8 | Rafael Villagómez | Van Amersfoort Racing | 1'48.470 | 0.458 |
| 9 |  Alexander Smolyar |  MP Motorsport | 1'48.557 | 0.545 |
| 10 |  Juan Manuel Correa | ART Grand Prix | 1'48.642 | 0.630 |
| 11 | Zane Maloney | Trident | 1'48.736 | 0.724 |
| 12 | Victor Martins | ART Grand Prix | 1'48.782 | 0.770 |
| 13 | Jonny Edgar | Trident | 1'48.795 | 0.783 |
| 14 |  David Vidales | Campos Racing | 1'48.802 | 0.790 |
| 15 | Reece Ushijima | Van Amersfoort Racing | 1'48.802 | 0.790 |
| 16 | Kaylen Frederick | HitechGP | 1'48.869 | 0.857 |
| 17 | Caio Collet | MP Motorsport | 1'48.889 | 0.877 |
| 18 |  Niko Kari | Jenzer Motorsport | 1'49.115 | 1.103 |
| 19 |  Nazim Azman | HitechGP | 1'49.125 | 1.113 |
| 20 |  Kush Maini | MP Motorsport | 1'49.188 | 1.176 |
| 21 | Pepe Martí | Campos Racing | 1'49.205 | 1.193 |
| 22 | William Alatalo | Jenzer Motorsport | 1'49.270 | 1.258 |
| 23 | László Tóth | Charouz Racing System | 1'49.445 | 1.433 |
| 24 | Francesco Pizzi | Charouz Racing System | 1'49.475 | 1.463 |
| 25 | Hunter Yeany | Campos Racing | 1'49.557 | 1.545 |
| 26 | Zak O'Sullivan | Carlin | 1'49.570 | 1.558 |
| 27 | Ido Cohen | Jenzer Motorsport | 1'49.641 | 1.629 |
| 28 | Ayrton Simmons | Charouz Racing System | 1'49.708 | 1.696 |
| 29 | Enzo Trulli | Carlin | 1'49.724 | 1.712 |
| 30 | Brad Benavides | Carlin | 1'50.193 | 2.181 |
| View full results | ||||
