Hi Melissa,
There is no reason that a breastfed baby cannot be fed while on it's stomach:
 mom can recline or lay on her back, place baby on her belly, and support the
breast with her hand to prevent it sliding off to the side...or baby can be
fed in bed while sidelying if the defect is small.
To fingerfeed a prone baby:  mom holds her arm in front of her body, palm up,
arm parallel to the floor. She supports baby's chin in her palm, with the rest
of the arm supporting baby's body.  Mom can rest her arm on her chest to
reduce fatigue.  The fingers are lined up with the mouth in this case, slip
one in and then insert the tube with the free hand. (I prefer tickling the lip
as with the breast to encourage the baby to DRAW the finger in, better
practice for latching onto breast). Using a 5fr feeding tube and a syringe
might work better than gravity feed devices.  Mom should be instructed to push
the plunger slowly (about 1/2 cc per suck) only while the baby sucks.  She
should rest while baby rests, to allow proper cardiorespiratory physiology.
Hope you can picture this, I'm much better at demonstrating these things than
describing them.  By the way, prone feeding is helpful for severely hypotonic
babies as well.
Catherine Watson Genna, IBCLC  NYC  [log in to unmask] (Vinny called nursing
"Umm" (rhymes with yum);  Alyssa said "I want mulk".  When in hostile
territory, I could say "we have milk at home" meaning we nurse at home, not
here.  No one was the wiser.)