Some course are built by snowcats, it involves pushing up successive lines of snow (imagine speedbumps top to bottom), and then coming in from the side and staggering the lines until you have a "checkerboard" pattern. Then you need lots of skiers to sidestep, then sideslip, the bumps. Then they ski them, slip them some more and away you go.
They used to make "perfect" courses, but now they will intentionally change the spacing to promote changes of pace in the turning.
Lately more and more courses are built by simply grooming a run and setting some short gates for everyone to ski around, less work and pretty mush the same result.