You fill the hole by the fence. The next morning there is another one in almost the same spot. Before trying to stop the digging, ask what that spot offers your dog: cool ground, a scent, a place to bury a toy, or a way to get past the fence. The answer changes the fix.
If the hole is along an exit route, check the boundary first and supervise yard time. Don't leave a dog alone with an escape route while you test a training plan. If your dog is digging to lie on cool soil, make sure they have shade, fresh water, and a comfortable way indoors. Heavy panting, weakness, or distress in hot weather needs urgent veterinary advice, not another garden project.
Give digging a legal address
For a dog who enjoys moving soil, set up a small digging spot away from the fence and plants. A container filled with suitable soil or sand can work. Hide a few treats or a safe toy just under the surface and show your dog where to find them. Supervise until you know they won't eat the filling or pieces of a container. When they start to dig elsewhere, call them over to their spot and make that spot worth choosing.
An indoor dig box with scrunched paper and scattered treats can help when the yard is not available. Supervise homemade enrichment and remove small pieces your dog may swallow. Digging is not a moral failure, redirecting it often works better than guarding every square foot of lawn.
Change the routine around the holes
Take note of when it happens. A dog left alone for long stretches may need company, walks, play, or more to investigate than an empty yard. A dog digging only when you leave may be showing distress, which calls for a different plan from ordinary digging, speak with a veterinarian or qualified behavior professional if you also see panic, attempts to escape, or self-injury.
Keep your dog with you or in a secure area while new plants take root. Protect hazardous plants and garden chemicals, and check for buried hazards before letting your dog dig anywhere. You are not trying to make your dog forget how to dig. You're making the safe place the interesting place. If your dog needs more satisfying outlets, the high-energy dog activities guide offers more ideas, keep any digging area free of chemicals and hazards
Sources: Dogs Trust: How to make a dig box and garden dig pit. Dogs Trust: Keeping your garden dog-friendly. Dogs Trust: Destructive behaviour in dogs.