IO plate for GIGABYTE GA-Z77X-D3H (rev 1.1) - I think it would work on other revisions as well.
Fusion 360 project: https://a360.co/2HJfZyb
Printed flat side down with no supports, material and quality don't matter because the print is so basic.
Once IO plate is placed in case it doesn't stay "fixed" and has a bit of wiggle, but once the motherboard is in, it's not an issue. Could improve this by taking inspiration from https://www.thingiverse.com/thing:3476969, but the first print was good enough.
Rotate object so that "inside" face of the plate is facing down.