Don't worry about what 'shotgun' means. I've managed to do precisely the job you're now planning, without knowing.
Get yourself a drum of cable like
this (that one comes with a couple of f-connectors as well, which you will need), run your cable, tack it in place, trim to length and fit f-plugs on either end. Then screw one f-plug into a spare terminal on your LNB, and screw the other one onto the 'LNB IN' terminal on the back of your Freesat box. Job done.