Question

how does a cover slip help in making a slide

Answer 1

The main function of the cover slip is to keep solid specimens pressed flat, and liquid samples shaped into a flat layer of even thickness. ... The cover slip can be glued to the slide so as to seal off the specimen, retarding dehydration and oxidation of the specimen.

Answer 2

The coverslip helps to spread the specimen evenly and also cover the sample so that it does not get spoilt.