molds for a Fiber glass box-

Ok this has probably been asked before but help me out!!!! Ok i understand the comcept of getting the mold of the box, but as FAR as making the MOld for the top of the box, like getting the strange MOUNTing angles foe the sub. How would you go about setting that up?????? any help would be great!!!!thanks 02 HOE 4 Audiobahnn AW1506ts 3000 watts