Ewan's favorite way to fall asleep recently is the Australian style nursing position. The "Australian position" is when the mom lies down on her back and the baby lies face down on top of the mom. The baby can lie a little diagonal or straight in line with the mom. I like the Australian position better than side lying because he likes to kick me when side lying!
When Ewan was a newborn, I would lie down on my back and he would lie perpendicular across my chest and nurse. His feet would hang over my chest and not even touch the bed. Now that he is 18 months, he likes to lie in line with my body, snuggle his head in the crook of my arm. He puts one leg between my legs and bends the other knee so that leg goes across my stomach.
If he is nursing on my left side, he will snuggle his head into the crook of my left arm, and I bend my left knee to keep him from sliding off.
Also, he will sometimes flip his head from the outside (resting on my arm) to the inside (resting in the middle of my chest), without letting go of the nipple. I've been a little worried about this new position because sometimes his head presses on my breast. I'm nervous that it might cause plugged ducts or something. If it is uncomfortable for me, I make him roll his head back to the outside. He loves to fall asleep this way. Maybe because he can hear my heart beat when his ear is against my chest.
If we are co-sleeping, he will fall asleep in the Australian position, then I roll him off of me to side lying and slowly back away to give us separate sleeping space. Sometimes, if he wakes up during the night, he will climb back on to me.