Someone who "does" hair once told me that to avoid that "straight across" look, to comb the hair out/up and use a pair of good hair scissors to cut vertically into the hair. Not across the hair... like you are pointing the sharp part of the scissors into the hair (parallel with the strands). Do that and just sort of make random small snips into the edges of the hair.
My daughter has very long mostly straight hair, no bangs, so I can cut her hair at home. But she has a wave across the back (and it runs on the diagonal about halfway down her back, lol). I was told to use that technique on the ends of her hair, after I get it as even as I can and the length I want.