I don't think there are any free slipways on the Broads unless a member of a club.
Until I sold
Just 17 in 2018 she was moored outside the Pleasure Boat Inn at Hickling and I used to launch and recover her from the Parish moorings there. I think I used to pay £5 each use.
There was a political war in the village a few years ago that couldn't be solved by District Council or MP's intervention. The main issue concerned the control of the newly built village hall. Eventually the entire Parish Council was ejected at an election, who like a number of Broadland parish councils manage village moorings and slipways. Not quite sure who the contact is these days, but I suspect Google will provide the answer.
There's lots of pictures of the Parish moorings at:
https://www.seahawk17.org.uk/owners-slipways.phpI have also used the slipway at
Martham Boatbuilding and Development. There's a little about that at these pages:
https://www.gregafloat.org.uk/seahawk/2004launch.phphttps://www.gregafloat.org.uk/broads/2011rhiannon.php