I use a Dynarette cushion sometimes. They come in two sizes, and I bought the large. I simply sits on your leg.....does not require attachment to the guitar.....and the guitar rests on it. The portion that comes in contact with your leg has an anti-slip material, although with some pants I find that it tends to move a little. To remedy this, I simply lay a small piece of anti-skid "shelf liner" material down, and sit the cushion on top of it. Another piece of shelf liner material on top of the cushion, and the guitar is almost 'stuck' in place. ....and no possibility of any kind of damage to the guitar finish.
2017 Jason Wolverton spruce/maple, 640, "Luz Blanca"
2016 Kenny Hill New World Estudio 640, cedar
2015 Kenny Hill Performance 640, C/IR
2017 Kenny Hill Player Cutaway, 640, Sp