This may assist.
create a bounding box, then toolpath, surface, pocket rough .
Select the side surfaces or all of the surfaces and machine the entire body using a spherical ( ball type tool) with a small stepover ie: 10mm ball step at around 2mm 25mm ball step at about 4mm check to leave about 1,0 mm of stock to leave X Y and Z, tick any check surfaces ( do not machine surfaces) tell it the bounding box is the pocket boundary and use parrallel for machining in rough.
Do the same again using a finish toolpath and uncheck the stock to leave tab.
On my machine having historically done a few moulds this should take about an hour to do and by the way if on the finish toolpath you use a 0.2mm stepover it will clean the job up perfectly and not have a lot of machine scallop marks to remove by sanding.
Be interested to see the finished pics.