Purpose of hole in stove leading to oven
A simple Google search yielded the following 

https://www.shopyourway.com/m/questions/1019973

All ovens are vented one way or another. You would not want to heat up the air in a sealed chamber because of thermal expansion. It would explode due to the heat expanding because it has no way to vent. A vent is also needed to vent fumes and by products that burn off during the self cleaning process. 

A vent is necessary and should not be blocked