Alright, I was able to do this task this afternoon. I put a sun lounge chair in my backyard and laid down on my back, slipped my shorts off and took the pose like in that image, legs up and back, spreading so the sun would hit my hole. Felt a bit embarrassing being in that pose, but it felt good also. The warmth of the sun felt good on my hole at first, but by the end of the 5 minutes it was starting to get a bit warm down there.
This task went well all in all though, glad I have the space to do it at