The correct answer is by adding surface roughness to increase friction.
A rough surfaces pair will exhibit more friction in comparison to a pair of smooth surfaces, as the peak of one surface can fall into the valleys of the other, signifying that in order to maintain movement, either something is required to break, or the surfaces would be required to get somewhat push apart.
Rougher the surfaces, the more commonly hills will have to push apart from each other, and the steeper will be the hills. For the majority of the practical work, friction is caused by the physical roughness of the surfaces taking part.
