How about a ‘randomized’ slalom that is driver’s choice? By randomized, I mean changing the spacing between cones and/or offsetting some of them 2-3 feet off the center line.
The layout could be such that going one way through them could allow a faster entry but punish you on the exit from the element. Going the other way would punish you up front but allow a faster exit.
Barring that, how about a decreasing-radius 270 degree turnaround (with the overlap on exit)..