If you are looking to imitate a one-handed backhand, Dominic Thiem is the perfect model. Here are a few things to observe:
Thiem sets up early loading the body. In frame 3 he reaches the end of the backswing. The racquet head is pointing up, his torso is coiled and the hitting arm is straight. Observe the knie bend and level shoulders. He is in perfect balance. From there he starts lowering the hitting arm and reaches the lowest point by frame 7, where you can see the racquet way under the incoming ball. One of the things worth noticing is the distance to the ball. He is actually reaching out to hit the ball allowing him to swing the racquet in a circular path. His body is leaning towards his left side letting the momentum carry him. He has a long follow through opening the body as he finishes the swing and using the left leg to stop his lateral movement. Perfect!