Hey Rob, I thought someone offered this tid bit up earlier,
If you take somthing like modeling clay, push the lure down to the half way point,, Then when you add your casting material the lure will then be set to the correct depth. (dont forget the alignment pins)
When the resin hardens up, remove the clay or what ever you were using,
Use a release agent, put this on the face of the mold as well as the bottom of the lure. and the pins too.
Pour on your top layer and poof. be careful with the resin, it is harder but also brittle.
I hope that helps a bit.
More info is on 2 part molds if you use the search feature,