Funding would cover signage and basic site preparation.
No toilets or other facilities would be provided, as they were intended for self-contained camper vans only.
The trial would be policed by Catlins responsible camping ranger Scott Martin, who has been co-funded since December 2017 by the Department of Conservation, and by the Clutha and Southland district councils.
During debate on the matter, Clinton ward councillor John Cochrane expressed reservations about the trial.
He was concerned current regulations - under which freedom campers could park where they liked - would not allow a trial to be properly enforced.
"If you're not changing the freedom camping bylaw to reflect the situation on the ground, what's the point? Legally, they can still park where they like. All you're doing is setting up another three free campsites for these people, without even going through the proper resource consent process.
"All the evidence has shown they're takers, not givers."
Bruce ward councillor Bruce Vollweiler said the trial would allow freedom camping to be controlled.
He said a similar policy in Central Otago had proven effective, without a bylaw change.
Cr Cochrane said the Central Otago sites were a "blight on the environment", and only encouraged freedom camping.
Cr Vollweiler said the policy had stopped the uncontrolled spread of freedom campers.
"I propose we look at the results of this trial, and address the bylaw more formally when we have that information."
Acting council chief executive Jules Witt said staff would now plan the trials in more detail, before returning to the council for final approval before summer.