I've never used a purpose built DO fixture for forks (or rear stays), instead just a little squeeze on the slot to get a snug fit and I've never had a disaster (close though) but I'd feel more secure if I did so I'm going to build one. It's not a conceptually difficult thing to do but if you have one please post or link photos! I'm sure to pick up a worthwhile tip.

I used the fork and frame fixtures a few times in the past but both are a bit cumbersome and I can envision something simpler and applicable to both ends.