Every cast you make you should have a potential netting location decided. I try to stay out of the water while fishing but a good netting location in the water is a healthy way to land your fish.
First off dunk that net bag in the water to make it wet and have less chance of rubbing off protective slim coat. The rage these days are ghost nets. These also do damage to trout and typically are not deep enough to handle a large thrashing trout.
You are using a sharp hook to catch this fish. Hyper-vigilance is good when releasing trout but not fanaticism.
Second always net your trout head first. Trout do not have a reverse. They do often at the last minute have a burst of energy as you net them. This can cause over runs of the net unless you have the lip of the net slight turned up to thwart that last run.
Don't lay them on the net for a photo. They never hold still and you obviously need more out of the water time for the trout doing this method. Many die from this photo shoot.
The trout is in the net and many times is rolling or trashing. If using spinner it can be a very dangerous time for the trout. They can catch the spinner in the net and really do some damage to their mouth. Be quick to unhook the trout.
Of course a two hand hold is optimal but that means having a fishing partner or a tripod. That typically means more out of the water time for the trout with the tripod method.
Sit down or kneel at water level. Reach in that net and wet your hand as you do so and lightly grasp the trout and turn it upside down to unhook the trout. The upside down discombobulates the trout for a couple seconds.
I do not like the fine mesh bags of a measuring net. Flies and lures can easily get hooked and that thrashing trout can tear its face off.
The trout is unhooked. Return it to the net. Let it get calm in the net. Stick the handle of your net in the bank and ready your camera.
In cold weather it is even more important to be quick. The freezing temps can really do a number on trout's skin/gills/eyes.
Reach in the net wetting your hand as you do so and lightly grasp the trout with your left hand. Make sure your hand is back from the gill plate and away from its vital organs.
The two hand hold is best but you can't do it efficiently alone.
Tripod photos are shaky at best. The trout is typically out of the water too long for this method. If the trout wants to leave let it go. A death grip is not an option.
Extend your arm and snap one photo and set it free. If the trout thrashed while taking the photo simply guide it back into the net or set it free.