Binoculars are best held and used with two hands for the sake of steadiness. You don’t have to be a binocular expert to know that, nor do you have to be an engineer to understand that binocular manufacturers design binoculars to be held with two hands. It’s obvious.
Still, there are a lot of us that hold and use binoculars with one hand, simply because we need the off hand to carry other gear. When I’m out birdwatching, for instance, I often carry my birding spotting scope and tripod combo over my shoulder and use one hand to secure and balance it as I walk, along. I can’t take the time to put the spotting scope and tripod down every time I see a bird, so I work my birding binoculars with one hand as I balance the scope and tripod on my shoulder with the other hand. In a similar fashion, hunters use one hand to work their hunting binoculars because they are carrying a bow or a gun in the other. Using a binocular with only one hand takes a little practice, but it works.
The only requirement as far as a binocular that can be used with one hand is an easy to turn focusing wheel. The binocular must easily be focused with one or two fingers of the hand that holds the binocular. This is a feature that is often overlooked when it comes time to buy a binocular, but if you plan to use only one hand to work your binoculars, it is critical to success. Unfortunately, it’s not something you can look up in a spec table and there can also be a lot of variation as to ease of focus from one sample to the next on the same model of binocular. The good news is that most binoculars, these days, get at least a passing score on ease of focus. Only rarely have I needed to return a binocular because I couldn’t focus it with one hand.