Place the five pieces in the 4×7 tray so that none can slide, individually or in a group.
This is a miniature in the style of Vladimir
Krasnoukhov's
Anti-Slide
puzzles.
George Bell, who mentioned anti-slide puzzles to me in 2015,
discovered that the pieces have a unique packing in a circle
whose diameter is approximately 5.6765 times the side of a piece cell.
Stable Boy was featured in the August 2020 issue of the Russian science magazine Квант.
You can sometimes obtain Stable Boy from Wood Wonders Online.