Lucky hen and good timing on your part to startle the coyote into dropping his victim. Good on getting the wound cleaned out right away. That should be the last time you use peroxide on it, though, as peroxide interferes with new tissue growth.
Also, kudos for recognizing the value of using the skin flap as a skin graft. It will cut the healing time in half. No, don't even try to suture or bandage. Use the wound ointment to "glue" the flap in place. I've found in about three days, the graft will begin to take.
Here's my wound protocol for a predator victim.
1. Treat for shock as the number one step. Give warm Gatoraid or mix a half teaspoon of sugar into a fourth of a cup of warm water with a pinch of salt and baking soda. Have the patient drink it all or syringe it into the beak.
2. Flush the wound well with saline. This is better than soap and water as it maintains the PH of the tissues. But warm soap and water will do. You need to wash away the bacteria from the wound.
3. Inspect the wound carefully. If it has a skin flap dangling, keep that. Do not cut it off. Look for bite, tear or puncture marks indicating a puncture wound. If you see this, the patient will need an oral antibiotic such as amoxicillin. Bacteria from the predator’s mouth can be injected deep into tissue and can kill in as little as 24 to 48 hours. You may want to try to obtain some amoxicillin from your vet to treat the bacteria that may have been left behind in the puncture wound.
4. Spray with Vetericyn wound treatment and let dry. Use a topical antibiotic ointment such as Neosporin or a generic without pain killer in it to coat the wound. If there's a skin flap, lay it across the wound that has just been coated with the ointment. Then smooth on a generous amount over the top of the skin flap to hold it in place.
5. It's useless to try to stitch a wound on a chicken. Don't even try. It's also useless to try to bandage a wound other than on the feet. The chicken will not tolerate it. It will be pulled off faster than you can blink an eye.
6. Clean the wound every day following the above steps. Keep the wound covered with the ointment. Never allow the wound to get dried out or it will not heal.