Michael - I've been uploading animated gifs not screenshots. Try opening the gifs in your web browser from the local file. It seems Dropbox only shows the first frame of the gif which is a pain. Can this forum allow URLs to embed images? I can't see anything relating to markdown.

I now tried doing this:

Select substrate
Under styles click on Red
Click on the eye next to Red to hide the substrate
Select the inlay parts
Under styles click on Blue
Click on the eye next to Red to show the substrate
Click on the right of Red to select it (yellow dot)
Click on boolean
Click on Done
Click on the right of Blue to select it (yellow dot)
Click on Done

but this results in the substrate becoming hollow rather than just having a pocket for the inlay. See this animated gif:

https://www.dropbox.com/s/xfiwwd4skf0wpm0/MoI3.gif?dl=1

File is attached.

Andy