I share with you my idea of standalone display+mainboard stand for ender 3.
It is compatible with stock Ender's display and SKR 1.3.
You can also use your stock Ender's fan (from electronic box downside your printer) - but mind, that it should blow from inside to outside :)

I think ventilation in this concept is quite good, my stepsticks are cold most of the time.
To make air flow even better I suggest to use some kind of "foots" for whole construction, to create air gap from the bottom.

Enclosure contains frame with holes for SKR 1.3, easy USB and card access, cable gap and even gaps for zip tie for elegant cable management.

Print in parts. Some supports are necessary, but really not much of them, proper alignment on print bed will allow you to avoid using much supports.

Two types of "top" are provided, either with and without hole for switch. It is regular switch from electric store. You can use it i.e. for LEDs control inside your enclosure.

BEFORE PRINTING: Please mind alignment on your print bed, uploaded STLs are not in their best positions, please rotate them (flat side down) for the best support optimization :)