So, for a project in my uni I built this reference board based off of the Analog Devices ADR4520 (or any other version of this chip would work really, provided you increase the supply as well). Since the thing quotes 0.02% initial accuracy, I figured it could be a good start for me into the world of volt-nuttery and wanted to do a good job, even though it's first application in the uni project was a 12bit ADC. Ofcourse, it's not anywhere near the 6.5/7.5/8.5 digit level of accuracy and drift, but it's a start for me, allowing me to at least verify the performance of some of my cheap-oh meters.
I woud like to know what needs improvement to make this an even better supply. One thing that comes to mind is that perhaps, using a buffer on the output would improve the performance. I don't know how essential things like cutouts between the pins for preventing stress due to thermal stuff is needed. I added a good amount of capacitance on the output but don't know if there is any reason why I would want to not do this? (note that there is a error in the schematic and PCB: the REG113 enable pin should be shorted to the VIN pin. I did it with solder on the final PCBs, but never got to update the actual schematic and layout).
PCB has a full ground plane on the bottom.
Schematic:

PCB:
