First, a belated welcome to the Cove!

We are sure glad you dropped by, and hope you tell your friends.
When you ask for an oven validation protocol, is this the FDA? Or, are you in the aerospace industry, and need to perform uniformity studies?
For calibration/ uniformity surveys, Jeff provided the "Handbook" so to speak, for the aerospace industry. That will let you know for your particular equipment how many T/C's, location, tolerance, etc.
For a validation, that is a little different story (for pharmaceutical industry); hence Harry's link. Your protocol should generally follow a pre-existing plan established for protocols. Per Marc's question, is this an IQ validation plan? or are you interested in temperature uniformity/ tolerance?
For temperature, you should place T/C probes uniformly throughout the realistic work zone, and verify deviation from the control probe, overshoot, recovery time, correlation to load probes, etc.