Several factors should be considered when determining the optimal location and design of a crossflow fan, including the model, design, and manufacturer's recommendations of the oven. Here are some suggestions to help you determine the optimal location and design of a crossflow fan:

1. Refer to the oven manufacturer's manual: Different oven models may have different designs and recommendations. Check the oven's manual, manufacturer's website, or contact the manufacturer's customer service for customer recommendations on the location and direction of the crossflow fan.

2. Evenly circulate warm air: The purpose of a crossflow fan is to ensure that warm air can be evenly circulated throughout the oven. Plan to place the fan so that it covers all parts of the oven interior to ensure that the food is heated evenly.

3. Avoid alternating hot and cold areas: Avoid placing the fan on one side of the oven, otherwise it may cause alternating hot and cold areas to form in the oven. If possible, place the fan on the back or top of the oven to achieve more even airflow distribution.

4. Consider the speed and frequency of the wind: The fan should be designed to produce the appropriate speed and direction of the wind. This ensures that the warm air can cover the surface of the food and circulate at a moderate rate to achieve a uniform heating effect. Some ovens may have adjustable wind speed and wind frequency, which can be adjusted according to actual conditions.

5. Experimentation and observation: Before using a new oven or changing the fan position and direction design, it is recommended to do some experimentation and observation. Try to place the ingredients in different positions and observe the cooking results. Based on the heating effect observed, slowly adjust the fan position and design to achieve the best cooking results.

It must be noted that the above suggestions are for reference only. The optimal crossflow fan position and direction design depends on the specific oven and personal actual needs. Always follow the manufacturer's recommendations and adjust and optimize according to your own situation.