Hello, I modified fan duct, so it fits new stock fan of Ender 3. I ordered mine Ender 3 in July 2019 and OEM 4010 didn't fit fan duct designed by ThijsRico, so I need to modify it. I give it to you guys, because I think a lot of you may have the same problem as I had.
You can print this with supports, but I printed it without any supports and it was all good. For fan attachment use two stock screws (M2x8), for attaching to base part use two M3x20 screws.