Historically, the way up from Royal Natal was via Basuto Gate, where Witzieshoek Resort is, or via The Neck (which is now closed to allow the trail to rehabilitate). This then brings you onto the Sentinel Car Park road.
In the days of Rydal Mount Hotel, the way up was via Namahadi Pass. The pass is still used by the locals, as well as another pass closer to the Chain Ladders. Both are accessed from the Fika Patso side.
Other than that the Amphitheatre Frontal climbing route, and it's variations, is approached via the Tugela Gorge. This is of course a climb, not a hike.
Someone also once described to me a scramble down the Inner Tower Gully, with an abseil needed at one or two points. Also not something which one would call a regular access point.