Hi Natalie, Though a level surface would be ideal, we understand that this is not possible for everyone. If your slope is not too extreme, it should be fine. We do recommend setting the slide up so that the water does not pool up against the base of the slide. It is better to have the outer rim of the splash area to be downhill from the slide. Please use common-sense safety practices at all times. If your location seems unsafe for any reason, do not set up your inflatable there. Sincerely, Blast Zone Support