Kettlebell floor press begins with seven points of contact: Heels, hips, shoulders, elbow of pressing arm.
Once weight is firmly set and begins to move, remaining six points are kept throughout the entire lift.
The “non-working” hand, much like in a stacked-hand kettlebell swing clean, is essentially a stabilizer bar, ensuring that the arm moves 100% straight and the fist stays vertical (not diagonal or horizontal); It is a kickstand, not a pressing assistant.
Elbow touches but does not smash the ground at the end of each rep, and a full, aggressive lock-out is neither a variable position or a suggestion.
Not dragging heavy weight across your chest or face while switching sides should be a given.