You should look at the object separately and in order

-first you look at the model and see which cavities will be totally ignored, as they will not be seen in the real life model

-then you analyse the model and see where the unavoidable slices will be and where parts must be made but separately sliced

-having done the unavoidable slices examine the model to see if you could go away using foam only or you will need another material for certain thin parts and so on due to lack of strength, etc.

-now having determined the materials and knowing your local supply thicknesses or what you have at hand slice the model accordingly

- then its the time to draw the locating pins as suggested and reflect them in the sliced geometry

As for making separate bodies from a single body its called "split" or "slice" . here is an tutorial how to do it by planes and here at min 1.30 is how to make the plane at an angle, cause certainly there will be parts that need to be done in separate slices


having done all that you will have to export the parts to your CAM and do them 1 by one and definitely using locating pins for the parts when you flip them as you will have to make some of them both sides.

Thats it.