I keep quail on deep litter. For our very occasional meat or fish leftovers, I have come up with the following modification of a maggot
bucket:
1. Find tall plant pot
2. Fill 1/3 with soil or
compost
3. Add scraps and leave for a day or so outdoors so flies can lay their eggs.
4. Fill up with
straw, hay or leaves. Leave where birds cannot disturb.
5. Check after 4 days depending on temperature, there
should be
maggots. When the food scraps have gone leaving just the bones, it's ready.
6. Place the pot on its side where your birds can get at it. They will scratch through and eat the maggots.
The soil below the scraps absorbs the stinky liquid the maggots execrete. The leaves/straw on top filters out the smell. If you miss the "sweet spot" and the maggots have pupaed in the soil, the birds will simply eat the pupae.
I have tested this with a portion of my quail as I had them get sick before from compost worms. This method depends on outside temperatures - works only in summer here when the flies are active. Soldier flies do not occur naturally here.