I've been in all sorts of different positions. My current esthetician has me do the knees to chest thing like this video. Others have been on all fours, to which my wife said "looks like the north end of a south bound mule" The one I'm most comfortable with is on my left side with my right knee drawn up to my chest.
Awesome, I’m getting done tomorrow by my esthetician. She’s an older lady (widowed) who I get along with really well. She gets very horny so we usually end up playing after.