I would not say it has to be EXACTLY level. You don't want it to be on too steep an incline. The first trip we started on we were in a steep driveway, started to pull the slide in and it went 'down the hill' so to speak and stopped! I pulled out of the driveway and it went right in!
2018 Flagstaff 832IKBS Travel Trailer.
2015 Silverado High Country.