Kneeling on all fours on the mat, is a great position.

Lean over your birthing ball. 

Place a pillow on your birthing ball and lean over.

Your partner could sit on the birthing ball and you can kneel down and rest you head on a pillow on their knees.

Robozo techinique  maybe used by your midwife to aid babies descent, at some stage of the birth if they are happy to show you.