If its a one off and you are making it from plate or bar the right thickness.
1
Hold it @ 1/8 deep in vise drill holes a bolt size(3/8 for 3/8-16), pocket through part.
Profile to @ .01 top of vise jaws then radius/fillet edges.
2
Take a scrap plate and drill-tap bolt pattern in it, bolt part down with 1st finished side down.
Profile down to match finished profile. Radius edges.
3
Unbolt part, open holes up to size on drill press.
If its many parts on 1st side, driil to size.
For 2nd side, make a set of profiled soft vise jaws to hold finished profile