I'm desperately trying to find a way to record realistic (well, believeable) stomach groans / noises for a short i'm working on. Basically the protagonist is suffering from severe..digestion difficulties.. and nothing i've been able to record so far has fitted at all.
At this point i'm going for the starve yourself for two days approach, but it is having a detrimental effect on the rest of the edit!
Get a nice sensitive mic and head on down to Chipotle's!
Seriously, that's a tough one. My first instinct would be to search through my sound library, but you probably don't have access to one. The most obvious way is to directly record a gurgling stomach. That happens all the time on VO sessions with sensitive mics. No need to starve for two days if you have a good sensitive mic. If you only have dynamics, well yeah, you'll probably have to be groaning real hard to pick it up well. Then the Chipotle might start to actually be a serious idea. This would give you a realistic sound, which may not be what you want, in a comical setting for example.
If I had to design the sound, I'm not exactly sure how I'd go about doing it, but I have a vision of myself over a kitchen sink full of water with plastic bags and bottles. I'd try and record lots of different kinds of bubbles. I'd probably edit the best ones together and downpitch and EQ them.
It's a proper sound design job, but I think it'd be worth it if the sound is important to your story. If it's just a filler sound, maybe don't spend too much time on it.
In addition to the good advice JC and John have offered, first find someone who naturally (or unnaturally) makes stomach or bowel sounds. Get them in a quiet space, feed them whatever they need and use a mic with a low selfnoise like a studio condenser. Also try a lav taped to their body near the noise making area.
Or, find someone who can make believable noises with their mouth and throat.