What's the easiest way to accurately drill the holes for mounting the motor without any sort of indexing head/table anyone?
errrr? i did a bit of a hatchet job on my first one (not having cnc at that point)
scribed a line with a centre finder square... dot punched my first two holes then used my vernier calipers (one tip in the dot) and scribed a circumfrence from both dots trail and error style :)

it got me there (just)

make sure you mark and drill the face that is going to sit on your motor just in case your drill wanders.... i find it really easy to forget stuff like that