Instructions
Fly to the Safari Zone.
Enter the Safari Zone building and Baoba will challenge you to catch a Geodude. Find Geodude in the grass in the area where you enter.
Talk to Baoba to customize the Safari Zone. There are six areas of the Safari Zone that can be added or removed. Add the "Mountain Area" to the Safari Zone.
Wait until morning. Larvitar will only appear in the morning.
Enter the Safari Zone and walk to the Mountain Area. Walk around in the grass until Larvitar appears.