Start out:

They’re in turtle
You’re on top on thier left side
Your chest is against their back.
You’re on your toes.

1. Wrap your back arm around their stomach, like the top starting position in wrestling
2. grab the lower lapel of their gi, this will limit their mobility and prevent them from rolling away from you quickly.
3. with your front arm, push thier tricep forward, moving their arm up away from their chest (giving your some room to slide your knee in.)
IF they do nothing:
4. slide your front knee in the space you’re created as you flop onto that hip and pull with your gi grip rolling them into your lap.
5. kick your left foot through and get the left hook first. You must get this hook first in order to avoid being put into half guard.
6. hook the back of their other leg with your other leg and elevate their right leg.
7. This will make them uncomfortable. release the hook. They will try to lower their leg, and when they do, take the other hook.
8. Now with reach over their shoulder with your left arm and clasp your left wrist with your right hand.
You now have the back.

IF they roll away from you:
Hop over them and drop your right knee beneath them.
Take the left hook first. (Do this with your left leg which will be top leg.)
then roll them to the left and pick up from step 6 above.