The 2007 world champion is not driving Thursday, but his teammate Antonio Giovinazzi is in command of the C38.
However, Raikkonen has not yet detached from Alfa's pre-season preparations on the penultimate day of the trials.
Images and a short video posted on his official Instagram account show the Finn doing a small repair on his seat just before his last day in the car on Friday.
Subtitled with the message "I did not go to school for nothing", the photos and video show that Raikkonen was modifying the left side of his seat and using a small grinding tool to complete the correction.
Raikkonen flourishes in his new, less political environment at Alfa, having signed a two-year contract with the team after five seasons with Ferrari.
He finished the second day of the second try, the fourth fastest, continuing well in pre-season testing.
His team-mate Giovinazzi is currently eighth fastest on the third day, 1.3 seconds off the pace set by Ferrari driver Charles Leclerc.