There is no safe way (to my knowledge) of getting in or out of a rumble seat unless you stand on the seat. I ask (demand) riders remove shoes first.
This link-
https://youtu.be/RBSCd2McCp8?feature=shared&t=39 will take you about 39 seconds into a video where you can see a nice lady I had just met getting into a rumble seat and taking a ride. She was absolutely THRILLED to finally ride in a rumble seat!