if you are getting slow airflow, then you can increase the surface area of the filter medium by either buying a thicker, pleated filter or, you can duct tape mu

if you are getting slow airflow, then you can increase the surface area of the filter medium by either buying a thicker, pleated filter or, you can duct tape multiple filters together in a cube shape with the fan being one side of the cube. That will give much more surface area for the fan to pull through.