I hung a plastic bucket over the chicken yard and put meat scraps in it. Since meat is not compostable, there's nothing else to do with scraps but throw them away. So the flies would lay their eggs on the meat and the larva would hatch. And when they were ready to burrow into the ground, like they normally do to metamorphose into flies, they would migrate down and find the holes in the bucket and fall to the ground, where I had placed an old sheet of plywood, and the chickens happily gobbled them up.

The meat scraps got gone, the chickens got fed, and the cleaned bones could be crushed and tossed into the compost.