The "Star Trek: Picard" star shared his hobby in an appearance on "The Graham Norton Show" via Skype alongside his wife, singer-songwriter Sunny Ozell.
Asked how he was spending his time, the 79-year-old actor held up a completed jigsaw puzzle for host Norton to see.
"This is one of my finished puzzles as you can see. It's actually framed because I framed them all," he said.
Stewart then showed off another example of his work and said, "Right here is one I just finished and I've got to be so careful because it's loose. This is a Frank Stella painting done as a jigsaw puzzle. This took weeks."
"It was very challenging because it's an abstract piece and that's what I spend a significant amount of time doing," he added.
The "X-Men" alum also spends his time reading one Shakespeare #SonnetADay during the lockdown to his fans and followers on Facebook and Twitter.
Besides Stewart and Ozell, 41, "Westworld" star Thandie Newton and actor-comic Ricky Gervais also appeared on the episode filmed remotely. RDSRDS