If there is a place your sure you DO want a hole dug go there and start clucking and scratching yourself, it's a riot, they will all join in. Throw a couple seeds in the bottom of the hole every few minutes and in no time they will be a foot down. Do not think that you can 'train' them to dig only where you want, however targeting their holes for the day can reduce the other damage.
Giving them something better to do works too, have you checked with the local produce market to see if you can have scraps? The toss out stuff in a pile for them to peck and scratch through will take up some of their time. A cabbage that you have put a screw into the core of so you can hang it up with wire or twine is a good game too, it's like a chicken's pinata, they party with that for hours.