That opening may be part of the appliance's designed ventilation. Warm airflow there is different from smoke, a burning smell or heat escaping through a damaged seal.
What the observation means
Do not cover the slot to reduce the draught or fit a decorative strip across it. The airflow can protect surrounding components and cabinetry. Its normal location and behaviour should be checked in the appliance instructions.
A useful next step
Record a significant change in the airflow or nearby surface condition. If controls become abnormally hot, the fan sounds distressed or there are electrical warning signs, stop use and arrange assessment. Never insert an object into the slot to check whether a fan is turning.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.