Unlike slots, flaps increase lift at all angles of attack.
As shown in the diagram to the right the maximum coefficient of lift CLmax increases with flaps. The zero lift angle of attack becomes much less. This makes sense since all the flap is really doing is increasing the camber of the airfoil.

It is important to note that when flaps alone are used (see diagram to the right) the stalling angle of attack decreases.

This means that the part of the wing with the flaps on it will stall before the part without the flaps.

Extending the flaps also increases the angle of attack of the wing for a given pitch attitude. The angle of attack is the acute angle between the chord line of the wing and the relative wind. The chord line is the imaginary line connecting the leading edge and trailing edge of the wing. As the flaps are extended, the trailing edge of the wing is lowered, increasing the angle of the chord line, and thus the angle of attack. When practicing a no-flap landing, the pilot notices the need for a much higher pitch attitude at touchdown as compared with a full flap landing.