This paper proposes a virtual keyboard that is used to type in characters by recognizing finger gestures with a low-cost camera. To increase the type-in speed, the proposed keyboard takes advantage of the freedom in hand motion. For type-in action with a single hand, the keyboard layer is selected at the same time as the type-in action. When both left and right hands are used for typing, an ambidextrous keyboard layout is proposed. In addition, an efficient type-in action is defined to speed up character input with both hands. An objective function is defined to formulate the type-in time and an algorithm is proposed to design a keyboard layout that minimizes the input time. Simulation results show that the proposed ambidextrous keyboard increases the type-in speed by 56.49% when compared with the right-handed keyboard.