How are induction motors designed to minimize cogging and crawling?
The answer to this related question may be helpful. In your link, you wrote "This can be easily overcome by making number of rotor slots more than the number of stator slots and by giving slightly slop to the rotor slots to the rotor slots (skewed)." The use of the word "slop" is totally incorrect and "slope" is not a word that is usually used in this context. What is meant is to arrange the stack of rotor laminations so that the rotor slots are "skewed" or angled with respect to the axis of rotation. Constructing the rotor with skewed slots and providing more (or fewer) rotor slots than stator slots is the remedy for both cogging and crawling. In your link, that statement is under the heading "Cogging." You should make clear that the statement applies to both crawling and cogging.

Further elaboration re comment:

The basic cause of crawling is a stator magnetic flux wave that is distorted rather than purely sinusoidal. Distortion can be caused by stator windings that are not well distributed among the slots, an insufficient number of stator slots, a poor relationship between the number of stator slots and rotor slots, or distortion of the voltage supplied to the motor.

Cogging can be caused by the number of stator and rotor slots being equal to each other or perhaps one being an integral multiple of the other.

The primary method of avoiding or minimizing these problems is to select an optimum number of stator and rotor slots and an optimum winding distribution scheme. In addition, it is helpful to select a skew angle for the rotor slots. The shapes of the slots can also be optimized to reduce flux wave distortion.

It is also helpful to design the motor so that the torque vs. speed curve is well above the rated torque for speeds below the rated speed. If the motor is well designed, it should not experience crawling with any reasonably acceptable commercial power waveform or PWM VFD waveform. There may be a bit more risk with electronic reduced-voltage starters.

Here is a bit more detail on the reason that distorted flux waves cause problematic torque variations.

Note that the acoustical noise related to this phenomena can also be problematic