The Petzl Podium is the classic, go to, work positioning seat for the discerning rope technician. When you have moved on from trying to modify skateboards and build DIY seats, you will wonder why you didn't get one of these years ago!
Not only do they look professional when you are using them, they are very comfortable and make a day in a harness much more pleasant.
The rounded sides prevent it from digging into your thighs, Three gear loops are available, one each side and one in the middle for your rope bag.
When not in use, it can slip up your back and sit out of the way until needed.