Rotate the filter top to be upside down.

Remove the 4 phillips head screws (red)

Remove the 4 phillips head screws (blue). These screws need a long/skinny screwdriver to reach, as they are sunk into plastic holes. But, they seem to be the same screws as the red screws.

Optionally, you can remove the 1 screw holding on the LED for the indicator on the front, and the plastic tab for the (presumably) particle sensing, but it is easier to reassemble if you do not remove those fasteners.