I have a midlock that is extremely easy to close one handed.
I point the knife so that the edge faces the floor, and use my thumb to depress the lever. Gravity pulls the blade down almost halfway closed, at which point it encounters some resistance from the spring. I then rotate the knife in my hand so that I can use my thumb to close it the rest of the way, making sure not to guillotine my fingertips.
With my Schrade LB-7 (similar to Buck 110), it's possible to hold it in an icepick grip, press the lever with my thumb, and then close it on my leg or something, but it seems a little clumsy and risky.