Hi Chris - check out the attached 3DM file for a version that should show you how you need to have it set up.

So note that I've added another object in there - there is a plane surface that is underneath the object that you want to morph. That's the base surface.

To do the Flow, start by selecting the object you want to deform, it should look like this (note only the object above the plane is selected, the plane underneath it is _not_ selected yet):



Then run the Transform > Deform > Flow command.

The prompt will say:



Now pick the plane underneath the object - that's what has been set up to be the base surface.

Then the prompt says:



Now go pick the curved surface on the inside of your piece where you want to place the morph onto.

That will produce this result:



There are a couple of different things that can trip you up a bit easily in this first beta - one is that this first version of flow works by matching the "underlying surfaces" which are sometimes larger than what you see on the screen if there have been some trimming or booleans done to them. If that's the case then you will need to use the ShrinkTrimmedSrf command to shrink those surfaces down to their trim boundaries. See this previous post for more info on this issue:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4442.6

That step won't be necessary in the next v3 beta - in the next v3 beta it will do that automatically.

Then the other thing is that in this first v3 beta it only matches between the base surface's natural UV directions to the target's natural UV directions, and if one surface for example happens to have its U direction going vertically instead of horizontally that can produce a rotation effect that you don't want. If you run into that then you need to rotate the base plane around or possibly flip it around its diagonal axis to get the U and V directions how you need them.

That also won't be necessary in the next v3 beta either because there will instead be a method that will match the UVs up according to which corner area you click on each surface, see this other post for more info on that:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4442.24

So anyway the next v3 beta will have some tuneups to make Flow easier to manage.

- Michael