Here's a diagram of the frame. It looks like two half-parasols with 3200 mm long spokes. The two halves are connected in the middle, as well as to the gun mount.
Crew installing the camouflage net. A standard net with 5 cm by 5 cm cells with green or white fabric patches is pulled over the spokes. Rope is used to hold together the camo net around the opening where the barrel of the gun is supposed to elevate.
After installation (top) the net is covered in additional camouflage material such as branches or straw (bottom).
The gun can fully elevate through the opening in the camo net and rotate freely. The camo net can be set up in 50-60 seconds and removed in 15-20 seconds by a well trained crew.