Depending upon which pack I'm using on the trip, I either just fold my Neo-Air into thirds width-wise and roll it up (just like how it came out of the box), rubber band it (no stuff sack) and place it wherever I have room in my pack. I make sure to pack it with soft non-sharp stuff, so it usually goes in between my quilt and my puffy jacket.
Or... with a frameless pack, I'll deflate it and often fold it up to fit the back panel area of the pack and slide it in (maybe even add a little air to it to stiffen up the "frame") to serve as part of a virtual framesheet with a cut down GG Nightlight pad.
I've often wondered how a NeoAir or other inflatable pad would handle just being stuffed into my pack, say, with my bivy, but have avoided trying it for fear of springing a leak from a crease or damaging a pontoon or whatever...
Curious to see what others do.