As mentioned, all this work is easier done on a square cut out than a carved body.. But im guessing your carving machine doesn't give you that option
Heres what i would try:
Make a 2 piece mold of the body with a hard material like bondo, making sure the edges are square... Open it up, mark/measure your holes and slot angle.. Close it up and carefully make your incisions
From then on... Clamp, cut, drill, next
Sounds too simple, so im sure im missing something??