You can use a cone to prevent the cat from licking, you can also put a bitter spray on the area t give the cat a bad taste whenever they try and lick.
When my cat got fixed we got a bitter spray to help protect the area, but my cat was so determined he licked right through the spray, regardless of the taste. We found that sprinkling some cayanne pepper onto the wound actually worked a lot better as the spice was just too hot for the cat to lick through and the taste was too much for him.
If you are looking for something simple, and cheap, try the cayanne pepper, just be very careful not to get it into the open wound. The vet told me, at last with the bitter spray, tocover the open wound with your finger and apply the spray around your finger, leaving the open wound without anything on it.
