CFraming a part to be a fixed height above the ground, corners included

I have an anchored part that shoots down raycasts on each of its’ corners. My goal is to position the part a fixed amount of studs above the ground and do it accurately, something like this:


The only solution to this problem I could think of is averaging all 4 raycast positions into one and then calculating an offset from it, however this does not produce accurate results.
I probably didn’t explain this well enough so if there’s any questions let me know. Any info is appreciated.

Forgot to mention, I already have the align to surface/rotation script down, I just need to know how to elevate the part properly