I didn't manage to sleep totally on my front as I was massive, but I did manage to lie partly on my side and front using pillows between my knees, to the side of my bump and behind my back. Imagine a kind of sideways recovery potision, one leg out to the side and one facing down, with both arms out to the same side as the leg.
I found it painful (bad SPD) to lie completely on my side as I got hip pain. Bump was so big that lying on back was completely out of the question (and I think not advised as it presses onto blood supply or nerves or something) so this was the only position I got any rest in.
Oooh, I was at the beach one day and a friend of mine dug a hole in the sand so that I could lie on my stomach for just a little while. It was heaven. I found no other way during two pregnancies, and I did suffer. Body pillows may be the way to go to relieve some of the hip pain.
I sleep on my front sometimes (39 weeks) but with one leg out to the side (knee raised) which takes pressure off the bump. I don't have a rock hard mattress though and have noticed I can't lie on the floor or on the garden in the same position, so if you do hae a really hard mattress you may not be able to.
If it could be done, I'm sure I'd have figured out a way by now. I was sleeping on stomach until about 22-24 weeks. Now 32 weeks and it's been completely impossible for the last month. I also have SPD and sleeping on back is too painful. I am in a giant nest of about 6 pillows and switch sides through the night.
I can get as far as being about halfway between my side and my front, with top leg flung over a pillow. Any further and baby presses into things or starts wiggling and kicking.