It's been 4 years since I last breast fed. But I successfully breast fed both my kids and also suffer flat nipples. I struggled with both. But nipple shields are your friend! I only used them for a a few weeks and then weaned the baby and me off of them and then exclusively breast fed both kids to 1 year. The nipple shields give the baby something to suckle on.
What you need to do is have the nipple shields bought and sterilised before birth. And have multiple sets of nipple shields so that you always have at least one set sterilised and ready to use. At least two sets in your bag ready to use, a couple of sets in the bedroom for night feeding, a couple of spares in case you drop one etc.
Then when baby is born, try to breast feed and if you struggle, then use the nipple shields. You will soon get into a routine, you simply pop the shield on before you feed.
After a few weeks, when I was confidently feeding and no more nipple pain etc. I started to wean us off using them.
I first of all used shields for a few weeks until we had feeding established. Then After a weeks, I would start a feed with the nipple shield and then after a short while (maybe 1 minute) I slipped the shield off and got baby back on immediately (it was a bit tricky for us both as the boob and nipple were a bit slippy as I had a lot of milk) - it was tricky but I persevered. If the baby didn't manage to latch on, I used the nipple shield again and then tried again at the next feed. I kept this up for a few weeks (starting off the feed with the shield and then removing and finishing the feed without the shield).
Once the baby was successfully feeding without it the shield, I tried to start the feed without the shield. It became easier, as the baby was used to my flat nipples by then and how to latch. And also possibly, my nipples were less flat as they'd been sucked for a few weeks! If I was unable to start the feed without it the shield, I used the shield again and then removed part-way through the feed. But I kept trying and eventually I was able to feed without the shields.
I thought second time around would be easier, but it wasn't. I still had to start with shields and wean us off them.
I am SURE that this would work for you too and I always like to share my story as it really worked.
I wish you the best of luck.