It is simple, just not simple enough for you. Your ignorance is unsettling.
http://www.wbur.org/hereandnow/2016/07/19/gerrymandering-republicans-redmap Read that and learn something, for once. You do not understand what gerrymandering is and how it works. You can look it up.
You can sculpt the districts into any shape you want and nearly any size. There is information available about your voting and it is by the household. They analyze where the pockets are and shape a district to cut out who they want out and who they want in. It is math system.
My district has ben redrawn a few times by the Repubs. as the population changes, the district is reshaped to get rid of the Dems. We have been a sure red district for many years.